USB stick data recording, blackbox-like housing?

[bwilson4web]

Hi,

I was following the recent Seawind 3000 crash in DeLand FL and noted that the aircraft was pretty much consumed by the fire. For rebulding N19WT, I am planning to go with three, external, RS-232 serial output, data recording systems:

Dynon 10A - electronic flight information system
Grand Rapids Tech EIS 2000 - engine monitoring system
fuel injection ECU - engine fuel injection system
My plan is to use one of my ordinary laptops to record the data to a USB stick but then I read about the fire destroying the Seawind 3000.

I'm now thinking the USB stick should be in a fire-resistant, water resistant, housing with just a USB extension cable to reach the laptop. As long as the data is saved to the USB stick and it is reasonably protected against fire and water, there would be a record of what happened. So I started looking for ruggedized, fireproof and water proof housings and there isn't much out there.

As a quick hack, I'm thinking a short, steel pipe with two caps. The cable would exit via a small slot cut into the pipe or one of the caps and everything inside wrapped in glass cloth possibly micro-epoxied. The idea is to have enough thermal protection to resist a short-lived fire. Adding a voice recording file, it would pretty much have everything found in a real blackbox.

Unknown is how much heat needs to be removed from a USB stick in normal operation . . . otherwise the housing becomes a fatal, oven for the USB stick. However, a thermal fuse (aka. low temperature solder) could provide a thermal path that in a fire would melt, reducing the heat flow to the USB stick. There are other one-way thermal systems (aka., bi-metal links) that could allow heat flow out but isolate fire generated, high-temperatures from cooking the USB stick. Without power, most electronics can handle fairly high temperatures.

Thoughts?

Bob Wilson

[cluttonfred]

Since weight is always a factor, I would think that lightweight metal box with ordinary loose fiberglass insulation and the drive itself wrapped in heat-resistant, heat-reflective tape would be a simple, rugged solution. You are right that the weak point would be the thermal bridge provided by the wire. Some sort of wireless set-up (a Bluetooth connection?) would be a way to avoid the wire altogether.

[steveinindy]

There are other one-way thermal systems (aka., bi-metal links) that could allow heat flow out but isolate fire generated, high-temperatures from cooking the USB stick. Without power, most electronics can handle fairly high temperatures.


So far as I am aware, the commercial variety use a coupling that shears the power at about 4 g of impact force.


Since weight is always a factor, I would think that lightweight metal box with ordinary loose fiberglass insulation and the drive itself wrapped in heat-resistant, heat-reflective tape would be a simple, rugged solution.

Yeah.....ever seen what happens to fiberglass at the temperatures seen in your standard GA post-crash fire? It melts (why do think so little is left of Cirrus and other composite aircraft after crashes?) and your suggestion . If I were going to do this (and the thought has crossed my mind on more than one occasion), honestly your best best is to copy the housing used on real FDRs and CVRs. The data unit is housed in a ceramic housing filled with water with a wax-sealed or thermoplastic-sealed vent hole to allow the water to boil off carrying some of the heat with it. Then you wrap the thing in a steel casing. Pretty much any other metal is going to wind up being destroyed in a post crash fire or by the impact itself.

No need to go reinventing the wheel when you can just reverse engineer what has already been done. In other words, just pretend you're working for a Chinese company.


I am planning to go with three, external, RS-232 serial output, data recording systems:

Dynon 10A - electronic flight information system
Grand Rapids Tech EIS 2000 - engine monitoring system
fuel injection ECU - engine fuel injection system


I would strongly, strongly suggest adding a cockpit voice and/or video feed. The voice feed would be simple enough since you could simply add in an intercom system with an extra "line" and use that to feed the CVR.


Some sort of wireless set-up (a Bluetooth connection?) would be a way to avoid the wire altogether.

KISS. The wire problem is able to be overcome in much simpler and more reliable ways.

[Frank Giger]

My first thought is that the pipe isn't such a bad idea if it wasn't for fire.

So why not get it away from the aircraft?

Let's say it's positioned near the tail at the top of the fuselage in a recess that's fabric (or otherwise) covered, spring loaded with a ten foot coil of wire attached to it, and that the spring is held compressed by a temperature released material. This could be as un-exotic as a cable tie that would melt.

If the plane wrecks and no fire, recover the stick.

If the plane burns, the tail is the last to go, and the stick sproings towards the back, away from the aircraft. The cable to the usb disconnects and the wire keeps it easy to find.

In all metal aircraft, one would think positioning it near the tail would be enough to keep it cool enough not to need the Emergency Sproing Device (tm).

[cluttonfred]

I like Frank's spring-loaded disconnect idea a lot, seems very simple and doable. Even without having it actually spring away from the aircraft, it would break the thermal bridge at the wire. It wouldn't be hard to come up with an insulated metal box over the USB port, with spring-loaded covers. The top cover you open to add or remove the drive, the bottom cover would be propped open and spring shut if the cable tie melts and pops the box away from the surface.

[steveinindy]

In all metal aircraft, one would think positioning it near the tail would be enough to keep it cool enough not to need the Emergency Sproing Device (tm).

You'd be surprised. ;) I do like the idea of the ESD though.


If the plane burns, the tail is the last to go, and the stick sproings towards the back, away from the aircraft. The cable to the usb disconnects and the wire keeps it easy to find.

Here's my thought though.....

You have an aircraft moving forward at say 70 knots that hits the ground. If the device is triggered to "sproing" on impact, you have to have enough force to propel it rearwards against that momentum. If you wait to deploy it until after the aircraft has stopped, you have a real chance of the trajectory being towards either the fire (plenty of aircraft tend to have their tails come "over the top" or pointed straight up as a result of the crash sequence) or having some form obstruction in the way that would minimize clearance.

My suggestion to make it easier to locate would be to not rely solely upon the wire but to have some form of really obnoxious sound device that could be easily shut off by first responders. Thing about a human hearing range version of the underwater pingers used to locate commercial data recorders when they wind up in water....

[martymayes]

Who is going to tell an investigator they should be looking for a data recording device?

[bwilson4web]

I like Frank's spring-loaded disconnect idea a lot, seems very simple and doable. Even without having it actually spring away from the aircraft, it would break the thermal bridge at the wire. It wouldn't be hard to come up with an insulated metal box over the USB port, with spring-loaded covers. The top cover you open to add or remove the drive, the bottom cover would be propped open and spring shut if the cable tie melts and pops the box away from the surface.
I had not thought of this but it is a good idea. There is no requirement that every data recorder survive every crash when most of the accidents (by gross numbers) are in light aviation. The performance specifications for a light aircraft data recorder are not the same for a +12,500 lb GW vehicle which tends to crash less than an order of magnitude than light aircraft.

So now I'm thinking 'ablative' coating and a rudder/tail mount. It doesn't have to survive every crash but enough that we can start to get a statistically significant sample. Did the Seawind have an engine failure? What were the engine metrics?

The only source would be the pilot in ICU and possibly the passenger. You don't suppose they might have been 'pre-occupied' during the emergency?

For my project, I have no problem with making two, ablative coated, USB sticks and mounting them on the tail-wheel spring. I don't even have to change them out unless I have a question about a recent flight and I'll have all of the early flights on that stick.

This is not a hard problem to solve.

Thanks,
Bob Wilson

[steveinindy]

Who is going to tell an investigator they should be looking for a data recording device?

Just mark the thing like is laid out in the AC/FAR regarding recorders. If you do that, it'll be identified most of the time.


I have no problem with making two, ablative coated, USB sticks and mounting them on the tail-wheel spring

You might not want to mount it somewhere prone to shock loading (inadvertent disconnection from the power source if you have a shear mechanism built in) or vibration as this can negatively affect data recording or device longevity. Given my choice in a small plane, I'd argue for either a mounting in the tip of the vertical stab or the tail cone.

[Frank Giger]

Of course we need to back up and think of what the design requirements are.

If it's to be a true "black box" that can stand everything but a nuke strike we're in trouble in a GA aircraft as it's going to weigh a ton and cost a fortune.

However, let's think more along the lines of the typical GA wreck, where the aircraft is largely intact first and then contemplate fire.

The ESD works great in the forced engine out, spin on turn to final, and CFIT wrecks where there is no fire.

For fire, how much does one need to design for? Fifteen hundred degrees? Twenty five hundred? And for how long?

Designing for 100% recovery seems like a dead end to me; a 70% recovery rate would be acceptable in my eyes as a production product for GA aircraft. If a plane were to crash into a building and the whole thing roast it I wouldn't expect recovery.

[rwanttaja]

Actually, I'm not sure how fancy you really have to get. I've seen several accident reports where the plane was well and truly hammered (and toasted) and the NTSB was able to access memory in ordinary components.

I'd wrap the thing in fiberfax and stuff it in a steel box. Electrically, I'd have a USB jack outside and a USB socket thermaly isolated from the shell inside. Connect the data/power lines with teeny tiny wires (hopefully, they'll melt before transmitting too much heat to the thumb drive).

Next problem... :-)

Ron Wanttaja

[Eric Witherspoon]

Of course we need to back up and think of what the design requirements are.

To me it read as if Bob wanted to design something for his personal aircraft, not as a GA product, to be sold/installed on any other aircraft. As such, one requirement would be that it would survive the accident Bob's aircraft gets into. Hopefully, that's none, but hope is not an engineering strategy (at least not a very successful one).

So, to "fire proof", let's look at the FAA's defined aircraft certification requirements. It took me a little searching to remember exactly where it was, but it's in 23.1191. Fire proof = 2000 deg. F (+/- 150F) for 15 minutes. So, there you go. If you want to ground-test this housing/device, get your 2000F flame and blast it for 15 minutes. If the data can still be extracted, that's a winner. If not, USB sticks are cheap; try again.

On the tailwheel spring - I agree with Steve - that's going to beat the snot out of whatever you have on there.

Really you're just talking about the ultimate "one shot" device - it survives the one accident which totals the aircraft. So no small part of this will be luck. I might put it inside a wing tip, especially if it's a tank-in-fuselage design. Because if the airplane goes into trees, wings will likely separate from the rest of it. Or if it burns up (especially if they are just metal wings), there's not much to burn in the wing tips, unless it's a tip tank design.

I might not even bother with much in terms of environmental protection - maybe a "ruggedized" plastic box of some sort - if you think a water / wet situation is possible (or just to keep it dry while washing the plane, if the mounting location isn't sealed). Think of the ELT - not that these are the most reliable thing in the world, but they've been certified inside a plastic box sealed with an o-ring. It's light weight and relatively low cost. Also reasonably accessible for changing the battery.

Now if it was intended to be mass produced, and the company producing/selling needed to ensure / guarantee some level of reliability - that might drive a more substantial solution. But for a single airplane, super-extreme-ruggedness = too much weight & too much cost, especially since whatever the solution is must be completely funded from design, build, test, and implementation by one person, for a production run of one.

In my airplane, I could see a little internal bracket next to the aileron bell crank access cover - so no new holes in the airplane, and the cover is on the bottom of the wing, so it's probably pretty dry in there most of the time, and it's out away from the fuselage (where the fuel is), and it avoids the previously discussed issues with being in the tail. Maybe even put a label on the bottom of the wing there, so if someone else ends up having to do this investigation, there would be some clue that there's something else inside the wing there.

[steveinindy]

Actually, I'm not sure how fancy you really have to get. I've seen several accident reports where the plane was well and truly hammered (and toasted) and the NTSB was able to access memory in ordinary components.

I'd wrap the thing in fiberfax and stuff it in a steel box. Electrically, I'd have a USB jack outside and a USB socket thermaly isolated from the shell inside. Connect the data/power lines with teeny tiny wires (hopefully, they'll melt before transmitting too much heat to the thumb drive).

Next problem... :-)

Ron Wanttaja

Find me a way to make a system track the control inputs, accelerometer readings, pitch, roll, yaw, etc and record them in a quick access recorder (QAR) or FDR. Not only would this be helpful in the event of a crash, it would also make flight testing much less stressful.

[Ron Blum]

This is definitely one of the best aviation topics I have seen. To the person that is even remotely thinking about developing something like this, I say without a reservation, "Go for it." Forget regulatory compliance. Any development is great progress. You have a great opportunity in a fairly unregulated sector of aviation to dream and develop as you desire. A lot of good aviation progress have come from ideas/concepts like this. For example, look at Electronic Flight Bags (EFBs). They were/are a pain in the rear to certify, but when started in the 14CFR23 (FAR 23), uncertified use arena, they took off like wildfire. And now they are common, everyday in the 14CFR25 world. The same is true with Garmin and the original 430s (which weren't originally approved for navigation and IFR use). Garmin changed how the industry operated. The iPad is doing a similar upgrade. YOU can too!

[bwilson4web]

Find me a way to make a system track the control inputs, accelerometer readings, pitch, roll, yaw, etc and record them in a quick access recorder (QAR) or FDR. Not only would this be helpful in the event of a crash, it would also make flight testing much less stressful.
Support for flight testing is one of my primary goals. Then I realized this is 90% of the data needed in a crash or failure analysis. But I'm sitting on the fuel tank in my plane, N19WT so a fire is likely to destroy the cabin. Also, it is a foam and fiberglass plane and I don't know how they handle fire. Certainly the Seawind 3000 went to ashes.

Another desirable task is an electronic logbook for the plane. The first owner and builder was very good about keeping the aircraft log current. The second owner was more detailed about changes but not so good about recording flights. This is 2012 and having an automated, electronic log book, especially one with detailed engine and flight data, means the flight testing extends to every flight.

I'm not sure how I'll handle making the USB storage 'ruggedized' and I do like the idea of a remote location (aka., rudder/tail or wing-tip.) Of the two, a tail-cone/tail-wheel spring/rudder fin mount would be easiest and looks to be "good enough." Mounted at the root of the tail-wheel spring, it should be relatively protected from vibration yet easily accessible.

My aircraft maintenance log will be part of the 'home papers' and documented USB stick. Unless I crash into my house, it will survive. <grins>

One last thought, it is very easy to 'blame the pilot' for accidents, especially the fatal ones. It means no one has to understand if carb ice or other equipment failures might have contributed to the accident. The only data we have about aircraft accidents comes from the accident investigations but they have limited time and budgets. An integrated, electronic aircraft log could be a 'game changer.'

Thanks you for everyone's insights,
Bob Wilson

[steveinindy]

But I'm sitting on the fuel tank in my plane,

Do tell why?


lso, it is a foam and fiberglass plane and I don't know how they handle fire.

About as well as you would expect. Also remember that a lot of the foams homebuilders like to use dissolve when they come in contact with a solvent such as gasoline.


Mounted at the root of the tail-wheel spring, it should be relatively protected from vibration yet easily accessible.

I would still recommend against that location.

[Bob Dingley]

Sounds like there is a need. Fortunately, a commercial product has been available since 2004 or earlier. While high end A/C have FDRs installed at the factory, there was a need what you describe in the single engine A/C. The company that I worked for bought some for about $5K each. They were moved from airframe to airframe out on the line as needed. They are self contained except for a GPS input and the card can be read out by the Flight Operations Quality Assurance (FOQA) director at a PC.

$5K might be steep for an individual, but there may be an opportunity for someone to rent these out to the masses. Maybe group ownership? The brochure indicates the features and may give folks some ideas. http://www.appareo.com/wp-content/uploads/Appareo_Systems_Vision1000.pdf

Bob

[steveinindy]

Thanks Bob. That is a really interesting system there although, as you say, rather steep.

[Bob Dingley]

Steep it is. But I know couple of folks that could build one like it. The Audio/Visual feature is a new one on me. Ours didn't have it. I hear that the auto racing folks use it and it has some ag tractor uses. That has me bewildered.

They were regarded as "snitches" from the first installations. Proven when a pilot was called in and his ferry flight was replayed for him. It was pointed out where he deviated 3 miles off course. It showed him tickling Vne at 200 ft MSL. This was where he pulled 2.1 G, 45 deg roll & 25 deg nose up. Coords plotted out to some lakeside camps. He got 30 days off.

[steveinindy]

he Audio/Visual feature is a new one on me. Ours didn't have it. I hear that the auto racing folks use it and it has some ag tractor uses. That has me bewildered.

There's been talk of cockpit video recording for years. There was a fair amount of resistance from the various pilot groups over concerns that the images could be leaked to the press or posted online, etc. I think it's a great idea although if I were to design a recorder it would have more data channels than what that has but then again that has a lot to do with my background as a crash survivability researcher so a lot of the data would not seem to make much sense to someone who isn't aware of the reasons for it being recorded.


They were regarded as "snitches" from the first installations.

That's the other reason why I think a lot of folks in the GA community are so hesitant to include even a cheap non-TSO'ed recorder on board. They view it as some form of invasion of privacy although I honestly think if we had them it would show that at least some of the crashes that are now put down to pilot error would turn out to be mechanical in nature, especially in the homebuilt community.

[bwilson4web]

Do tell why? (I'm sitting on the fuel tank. RJW)
This configuration puts the fuel tank in the middle of the CG range along with the extra seat. As the fuel burns off, the flight characteristics of the airplane do not change. Furthermore, as the aircraft loading increases with a passenger or passenger seat bag, the CG stays in the safe range.

Bob Wilson

[steveinindy]

This configuration puts the fuel tank in the middle of the CG range along with the extra seat. As the fuel burns off, the flight characteristics of the airplane do not change. Furthermore, as the aircraft loading increases with a passenger or passenger seat bag, the CG stays in the safe range.

Bob Wilson

Ah....that just doesn't seem like the safest choice. That was actually one of the first structural choices I made in designing both of the aircraft I have worked on so far. Both of them have well protected fuel tanks in the wings.

How much stroking distances do you have under the seats just out of curiosity?

[Frank Giger]

Steve, it's actually a pretty common solution for earlier designs of light aircraft - a bunch of WWI era planes had the tank under the seat for CG/maneuverability concerns.

Different question - would one need a glass panel for the USB data recorder to work, or could a small data collector box be made to support it for us Standard Six guys, with a little GPS receiver like the ones that plug into an iPad?

Mr. Wilson is right on the money with the flight testing goal - one of my concerns in the First Forty is being able to juggle recording information while flying what will undoubtably be a handful of an aircraft (short taildragging biplane). I sure would be nice to work out Vx and Vy info on a desktop computer after the fact, and to see precisely the stall speeds as well as temps.

[bwilson4web]

. . .
Different question - would one need a glass panel for the USB data recorder to work, or could a small data collector box be made to support it for us Standard Six guys, with a little GPS receiver like the ones that plug into an iPad?
Curious you mention the iPad. I have a Dual GPS-to-bluetooth receiver that works with the iPad. The sad news is I have not found 'track recording' app to record a trace. In contrast, the nuvi GPS receivers keep a track record that can be downloaded to a computer. But it is easier to just get a GPS 'mouse' connected to a laptop and stream the data to a file ... which could be on the USB stick.

In my Prius energy studies, I used a GPS mouse to calculate the kinetic and potential energy which I could correlate with OBD data from the engine. This gave me a total vehicle energy model to refine Prius operations.


. . .
Mr. Wilson is right on the money with the flight testing goal - one of my concerns in the First Forty is being able to juggle recording information while flying what will undoubtably be a handful of an aircraft (short taildragging biplane). I sure would be nice to work out Vx and Vy info on a desktop computer after the fact, and to see precisely the stall speeds as well as temps.
In my case, I had decided to replace the existing electro-mechanical instruments with MEMS based systems. This substantially improves reliability and accuracy. I was pleased to find it also comes with an RS-232, external data logging capability. But there is one thing I had not expected, increased interior volume.

This is the current cockpit, pilot's side:
http://hiwaay.net/~bzwilson/dragonfly/2012/DF7.jpg
Everything to the left of the Nav/Com goes including the panel and this becomes the access way for maintenance. In the remaining column, there will be the flight director, com radio, engine monitor, and throttle. It will also have a set of switches and electrical power monitors.

The pilot side rudder pedals and brakes will be moved forward about 4-6" while the passenger side pedals will optionally fold down. Short pilots are checked out in the right seat and longer legged ones in the left. All flight, engine, and power controls and instrumentation are in the center console for shared access.

I may move the center console stick to the left, it already has a passenger side stick. This makes it easier to mount any additional switches on the shared console space . . . and install the cup holders.

Bob Wilson

[Ron Blum]

If you want to record the six-pack, you must make them electronic first, unless ... Video actually works well, and you get 30 frames/second. Plus, you can record comments, too. For certification, we actually use video to determine electronic airspeed lag (yes, steam gauges (pneumatic instruments) actually have less lag than electronic instruments (PFDs) due to A-D converters and data buses).

The whole, inexpensive FDR concept is a GREAT idea. Record every data bus you can. There is a really cool program called LabView (by National Instruments) that has changed the flight test world as an "inexpensive", PC-based, few parameter recording tool. All data is good data.

As a word of caution, GPS data has drawbacks, but it will get one in the ballpark. Know how often the data is being output and the accuracy of that data. The flight test industry uses differential GPS and then time corrects that information.

[bwilson4web]

. . . For certification, we actually use video to determine electronic airspeed lag (yes, steam gauges (pneumatic instruments) actually have less lag than electronic instruments (PFDs) due to A-D converters and data buses).
I hadn't thought to check the response time of MEMS based instruments. Do you use hot-wire anemometers as the reference to check the delay and accuracy?


. . . There is a really cool program called LabView (by National Instruments) that has changed the flight test world as an "inexpensive", PC-based, few parameter recording tool. All data is good data.
You're right about the quotes! But I pretty much just use excel.


. . . As a word of caution, GPS data has drawbacks, but it will get one in the ballpark. Know how often the data is being output and the accuracy of that data. The flight test industry uses differential GPS and then time corrects that information.
The first 10 minutes or so, the GPS data wanders all over the place and the altitude data is worse. But after 10-15 minutes it settles down . . . or wanders less. Still, I'm curious about differential GPS.

When I was picking up N19WT, signing the final papers, a Cessna flew in through a drizzle, 40F, 500 ft. ceiling, and 20+ Kt wind. I know because I was loading the plane on the trailer that wet, miserable day. The pilot said he used a GPS approach. Still, I started looking at the WAAS and I see it covers large areas. I have GPS receiver options with the flight system so I'll see if any of them incorporate WAAS capability or the other systems without costing an arm and leg.

I'm a Day/Night VFR pilot and have no interest in IFR flight but I'm a firm believer in bi-annual, instrument training with emphasis on recovery from unusual attitude and being 'talked down.' I don't take off into known IFR weather but there are places between weather stations where only God and the pilot knows what is there.

Thanks,
Bob Wilson

[Ron Blum]

Do you use hot-wire anemometers as the reference to check the delay and accuracy?

I'll keep this as generic as I can, but if you want more information, just email me.

First, we calibrate the boom, airborne and on the ground ... the two calibrations are significantly different (and may differ with configuration/flap/gear/etc. changes, too). Booms are known for being INaccurate, but highly repeatable. Then we do an easy one to one comparison to the different aircraft systems.

For delay we use an analog transducer sampled at a very high rate (250+ samples/sec). We also do "balloon burst" tests. For accuracy we calibrate each individual transducer (leaving only repeatability) and run several different flight tests, some using GPS for enhanced accuracy.


You're right about the quotes! But I pretty much just use excel.

LabView is a PC-based program that allows you to excite and record instrumentation without a full-blown data system. We use a version of "Excel" for data analysis. too.



The first 10 minutes or so, the GPS data wanders all over the place and the altitude data is worse. But after 10-15 minutes it settles down . . . or wanders less. Still, I'm curious about differential GPS.

OEMs use a couple forms of Differential GPS (DGPS). One is a service out of Canada that transmits the error (I'll explain that shortly ... and it costs), and the other (more accurate) is self-contained but requires two GPS units. You are exactly correct in that the GPS signal settles down ... but only while the unit is not moving). Explaining the 2-unit DGPS, one unit is in the airplane (moving), and the other unit is on the ground (fixed). Since the ground unit is not moving, the error is the difference in where the unit thinks it is versus the fixed (known) location. The error can either be post-processed or transmitted up to the airplane. The Canadian service works the same way but is a little less accurate. To put these accuracies in perspective, the Canadian service is within 2 meters I believe. The 2-unit system is within 2 centimeters.

The recent issue of "Soaring" magazine has a really good article on how GPS/DGPS works.

fly-in-home@att.net

[steveinindy]

Plus, you can record comments, too

It has always amazed me how little panicked screaming there is on CVRs. Fair amount of cussing but it's a real testament to the pilots who handle the aircraft disasters caught on tape that they can maintain some semblance of a level head in situations like that.


The whole, inexpensive FDR concept is a GREAT idea. Record every data bus you can. There is a really cool program called LabView (by National Instruments) that has changed the flight test world as an "inexpensive", PC-based, few parameter recording tool. All data is good data.

But not necessarily valid data as pointed out by your next comment. ;)


I'm a Day/Night VFR pilot and have no interest in IFR flight but I'm a firm believer in bi-annual, instrument training with emphasis on recovery from unusual attitude and being 'talked down.' I don't take off into known IFR weather but there are places between weather stations where only God and the pilot knows what is there.


The problem is that a biennial instrument review is of little use to most people since the retention rate of the skills is generally pretty dismal. One can often pretty readily correlate the frequency of loss of control/spatial disorientation events in instrument-rated pilots by looking at their total instrument time and even more so the amount accrued within the past 30 to 90 days. Relying upon being instrument rated and having infrequent reviews is going to create a false sense of security in many people.

[steveinindy]

Steve, it's actually a pretty common solution for earlier designs of light aircraft - a bunch of WWI era planes had the tank under the seat for CG/maneuverability concerns.

There's also a reason why those aircraft had earned the nicknames "meat grinders" or "funeral pyres" among the pilots.

[Ron Blum]

A couple different replies as this thread has gotten split ends.

1A. (Good or bad) A lot of early (true) ultralights had fuel tanks that were designed as seats to save weight (to meet the 254 lbs. limit), but most were open cockpit with easy bailout capability. As time progressed (and as the "heavy" ultralights came into being), the fuel stayed there, but it got harder to get out of the vehicle. Remember what an ultralight's gross weight stall speed is supposed to be, though.

1B. Also look at a lot of the early light planes (yes, type certificated). The Champs, Cubs and Taylorcrafts all had header tanks. So, if the crash were nose down, the hot engine would be pushed back into the fuel tank. We have learned from these experiences, but as the saying goes, "The FARs are written in blood."

2. Bob has pointed out his limitations (and is conservative in a good way), which is the correct way to handle safety. You would be shocked at how many of the VFR into IFR condition fatalities happen to current, instrument rated pilots. The pilot (although rated) isn't ready for the transition, and it kind of freaks them out when they go IFR. If you don't believe me, I can tell you the "rest of the story" offline.

[steveinindy]

most were open cockpit with easy bailout capability

Also easy "forcefully ejected from the aircraft" capability. About 90% of the cases of pilots with impaled objects I've come across out of the 1800+ plus I have pathology or other medical records for are in ultralights. There's one sheriff in Tennessee likes to tell that he has an ultralight pilot in his jurisdiction who has been in five crashes that the sheriff is aware of and all of them involved trees. The irony is that the fact that the guy's first name is George.


If you don't believe me, I can tell you the "rest of the story" offline.

You know my e-mail.

[Frank Giger]

There's also a reason why those [WWI] aircraft had earned the nicknames "meat grinders" or "funeral pyres" among the pilots.

I don't plan on be shot at by flak or machineguns....and also to include an engine that doesn't throw castor oil and fuel all over itself as part of its design!

Thanks for all the conversation, folks; this has been a great discussion. I won't be putting in a black box on my plane (too expensive), but there's zero reason I can't put a camera on the panel, which I hadn't thought of!

[steveinindy]

I don't plan on be shot at by flak or machineguns....and also to include an engine that doesn't throw castor oil and fuel all over itself as part of its design!

Actually the comment I made was in reference to training crashes.

[Larry Zepp]

The USB data recorder is a great idea. To protect it from fire, you need the lightweight and insulating properties if an intumescent coating. This expands with the heat of a fire to form an insulating foam char that is 10 - 20X the original volume and can resist 1500-2000 deg. F. This is the same material that forms the outer coating of a fire sleeve used to protect an aircraft fuel or oil line.

This material is commonly available in "big box" stores as a special type of silicone RTV caulk called a "fire stop" or "fire barrier". It is used to block possible fire spread through wiring channels in buildings. It applies just like regular RTV silicone. Here is how you might use this to protect the USB flash drive / memory stick:
- seal the USB cable to the drive using an automotive high temp silicone to seal for moisture. Then use a stiff acid brush to apply several layers of the fire stop silicone around the flash drive and cable. Coat at least one foot of the cable for heat protection.
- pick a small box as a housing - go for high temp capability, such as steel or stainless steel, but keep it light. Paint the inside of the box with several layers of the firestop silicone. Avoid aluminum due to low melting temp. For extra temp. insurance, center the flash drive in the center of the box and pack it with vitamin gel caps (water). Seal the cable entrance with the firestop.
- Seal the box with the firestop, then paint several layers of the firestop on the outside of the box using the stiff brush. While you are at it, alsp paint several layers of the firestop in a piece of aluminum foil - for your own testing. Let dry and this should be very good protection and also light weight.

[Ron Blum]

Larry, great post! This is how we change the aviation world. Everyone in the certification world laughed at Garmin when they introduced the 430. Look at where they are at now ... and an order of magnitude less expensive. iPad applications might just do that again, too! I'm proud to be a part of this thread.

No pressure, Bob.

Blue on Top,

[bwilson4web]

Thanks Larry,

I had found a reference to this fireproofing material at a UK web site and I wasn't looking forward to having to order it. But it is good to know I should be able to find it at my local hardware store.

I'll put one together and test a USB stick with a temperature probe in ordinary use. If it works for 24 hours in active use while coated, the next step is to monitor the temperature in an ordinary fire in the BBQ without power. The temperature probe can let us know how hot it gets. This is just a 'sanity' test, not meant for any type of certification.

Bob Wilson

[steveinindy]

Actually knowing the way the FAA guys at Atlantic City love to set stuff on fire, I'm pretty sure if you asked they could talk you through (or provide the technical paperwork) on how to set up a "home game" version of the actual fire exposure certification tests.

[Frank Giger]

I've been turning this over in my head as a broader project - data recording.

Thinking that the product would be aimed at GA/homebuilding, it doesn't need to have the conprehensive data points as in commercial aviation. With that in mind, what should it record?

First blush:

Engine RPM
Oil temp
Oil pressure
Stick and rudder positions*
Mixture control position
Carb temp
Throttle position
Airspeeds - IAS and ground (the latter handled by GPS)
The flight profile could be handled by GPS, I reckon.

I don't know if voice recording is really required; maybe that's because I think it would be very boring to hear me chuckling on beautiful days and growling at a less than perfect touch and go.

Another question is data polling frequency. Maybe every second to save memory space?

* This could be done pretty cheaply and with little weight. It's a three Hall Sensors, and the polling and recording software is used in every decent gaming HOTAS and rudder pedal set.

[bwilson4web]

Hi Frank,
I've been turning this over in my head as a broader project - data recording. . . . Let's start a new thread as I have some 'lessons learned' to share from my Prius engineering studies.

Bob Wilson

[steveinindy]

Thinking that the product would be aimed at GA/homebuilding, it doesn't need to have the conprehensive data points as in commercial aviation. With that in mind, what should it record?

Can I request that a few accelerometers be tossed into the mix for the sake of crash survival research? Ideally, :
-At The center of mass of the aircraft
-In the back rest of each of the seats (ideally would be hip height, shoulder height and one in the head rest).

Measuring longitudinal, vertical and lateral accelerations.

[Ron Blum]

Frank: Good list to start with. I would add anything that's already on a bus as those are normally cheap and easy parameters. Angles of pitch and roll are always helpful, too.

Now that you've opened the can of worms, engineers and accident investigators never have enough data, but designers never have enough memory ... and nobody has enough money or can afford the added weight and complexity. This is sooooooo way cool.

Bottom line:
You are so on track with this one. Fantastic idea. I look forward to learning more in the new thread.

[bwilson4web]

When my 30 minutes, new-thread posting was lost when my internet connection went out, I decided to
reply with shorter notes:

I've been turning this over in my head as a broader project - data recording.

Thinking that the product would be aimed at GA/homebuilding, it doesn't need to have the conprehensive data points as in commercial aviation. With that in mind, what should it record?

First blush:

Engine RPM
Oil temp
Oil pressure
Stick and rudder positions*
Mixture control position
Carb temp
Throttle position
Airspeeds - IAS and ground (the latter handled by GPS)
The flight profile could be handled by GPS, I reckon.

I don't know if voice recording is really required; maybe that's because I think it would be very boring to hear me chuckling on beautiful days and growling at a less than perfect touch and go.

Another question is data polling frequency. Maybe every second to save memory space?

* This could be done pretty cheaply and with little weight. It's a three Hall Sensors, and the polling and recording software is used in every decent gaming HOTAS and rudder pedal set.

These are important and offer significant information:

Engine RPM - yes
Oil temp - for climb testing, yes
Exhaust temperature - yes
GPS - absolutely, first derivative is velocity, second is acceleration
airspeed - complements GPS to factor out winds aloft
I'm not so sure about these:

Oil pressure - cabin report is required but this really is the pressure relief valve
Mixture control position - calibration is a problem but EGT does a better job
Carb temp - cabin report for ice detection, yes, recording not so much
Throttle position - not so sure, fuel flow is better if available
Stick and rudder positions - not so sure, adds weight
As for sample rates, generally faster is better but run-length encoding solves the volume problem. Run-length means recording a data value and a counter about how long it remains within a narrow band of values. A simple compression technique, it saves a lot of space without spending a lot of CPU cycles.

I've found sub-second in the 0.1-0.2 range is about as fast as one wants to record. This is in the same time-scale as human response time so what one feels or does can be correlated to recorded events. Below 0.1 seconds is the range of vibration or engine tuning, not really flight recording. Above one second gets to be so coarse as to be difficult to find useful performance correlations.

Bob Wilson

[bwilson4web]

Can I request that a few accelerometers be tossed into the mix for the sake of crash survival research? Ideally, :-At The center of mass of the aircraft-In the back rest of each of the seats (ideally would be hip height, shoulder height and one in the head rest).Measuring longitudinal, vertical and lateral accelerations.Many personal devices like iPhone and iPad have three axis accelerometers and there are apps to record them. However, I've found they have a lot of 'noise' and 'drift.' They are OK for short events but not really useful for vehicle studies. A better approach is to use a Gulf Coast Data Concepts, USB Accelerometer.

I have two and used them in a Prius brake pause study. I also used one to confirm the physics of a Wichitech, tap-hammer. When I start engine and flight testing, I will use them to measure vibration of the engine vs engine mount and engine mount vs firewall anchors to look for resonances. In flight testing, I'll affix them to the elevator and aileron bell-cranks to look for the early indications of flutter and resonance. But for ordinary flying, I would use GPS recorded data.

Now if your interest is in accident G loads, mythbusters often uses shipping "G" force, one-time use gauges. These are small, light weight units that break or indicate the maximum"G" force experienced. I just Googled "shock timer" and "shock sensor" and got several hits.

Bob Wilson

[steveinindy]

Now if your interest is in accident G loads, mythbusters often uses shipping "G" force, one-time use gauges. These are small, light weight units that break or indicate the maximum"G" force experienced.

Yeah, that's not accurate enough to tell anything useful in terms of actual science. It will give you some vague ideas but we already have those.

[Matt Gonitzke]

I've found sub-second in the 0.1-0.2 range is about as fast as one wants to record. This is in the same time-scale as human response time so what one feels or does can be correlated to recorded events. Below 0.1 seconds is the range of vibration or engine tuning, not really flight recording. Above one second gets to be so coarse as to be difficult to find useful performance correlations.

Bob Wilson

I'll have to check my notes from my flight dynamics class in college, but I think flight test data is typically recorded at 30Hz, which is a lot more frequently than every 0.1 second. Unwanted background noise can be filtered from the data without too much trouble.

[Frank Giger]

I stuck carb temp in there because icing is almost impossible to ascertain after an engine-out landing (surviveable or not); the pilot that is aware of icing and can report it almost always also deals with it before he's engine out! The probes are readily available and not horribly expensive.

Stick and rudder position can be done at about an ounce or two, including wires - potentiometers are really light weight and small! You're right in that it's low on the totem pole - spins are a function of cross control and could be moot; I stuck it in as something I thought was pretty cool.

I'll also admit that I put oil pressure in there because it's a gauge on the panel as much as anything else.

I also agree that throttle position might be a less than optimal thing to measure; I put in mixture control position with the assumption that there isn't an EGT.

Dunno about accelerometers on seats - it might become a cost and installation nightmare.

I wonder if the computers they put in cars might be a good starting point, as they monitor a host of things and record it for download by mechanics (or at least errors - capturing the data stream itself shouldn't be that much a strain).

[steveinindy]

Dunno about accelerometers on seats - it might become a cost and installation nightmare.

It wouldn't be that hard and since it's not an "avionics" component, one would not have to use the more expensive TSO'd stuff.

[Ron Blum]

Data at 10 times/sec (0.1 sec) would be great. The original "in-the-background" monitors recorded at 1 sample/sec, and they where useful. Looking at today's flight test data won't help much as with sub and super-comming, the rates are typically customized between 1 and 10,000 samples per second depending on the parameter. On a funny note, when I started in Flight Test, we had to change tape reals every 20 minutes or so. Today we can fly for days (literally) and record 6,000+ parameters at a main frame rate of 250 samples/sec. ... and pull off a little solid state drive when we're done.

I vote for control positions and aircraft attitude. I still like your original list.

On a related but somewhat different topic, I think it would be great to go after the 3 big fatal accident causes: controlled flight into terrain (CFIT), VFR into IFR, and stall. With GPS we have the ability to eliminate CFIT, aural attitude reminders could catch most of the VFR into IFR scenarios (think Kennedy), and stall is a very simple, aural AOA indicator. What this thread is doing is fantastic; it's always great to know what happened. But it would be better if we could intervene before we loose another friend.

Bottom line: This thread topic is awesome, and YOU are how things get done. Thanks!