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Thread: Feedback Needed - Homebuilt Aircraft Cruise Speeds

  1. #1
    rwanttaja's Avatar
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    Feedback Needed - Homebuilt Aircraft Cruise Speeds

    I'm doing one of my periodic deep analyses of homebuilt accident statistics. One aspect is comparing the fatality rate for specific homebuilt aircraft against their configurations and cruise speeds. This is an example of the type of graphic I'm looking to update:


    Configuration is easy, but cruise speed is arguable. Below is my initial input to the analysis. I got them through a simple Google search. But I'm sure some folks here know better, and am interested in some feedback.

    I realize this is awkward, in that some types of airplanes (such as the Kitfox) have a range of models with a commensurate range of cruise speeds. But I don't need absolute accuracy...plus or minus 10-20 MPH is just going to shift a point on a plot slightly left or right.

    I figure it should be a popular topic. You get to argue about your favorite planes, plus you get to call me an idiot for some of my values. :-)

    Aircraft
    Cruise (MPH)
    Avid Flyer
    92
    Bowers Fly Baby
    85
    Bushby Midget Mustang 2
    165
    Cozy
    180
    Glasair
    220
    Glastar
    135
    Harmon Rocket
    230
    Kitfox
    110
    Lancair IV
    300
    Pietenpol Air Camper
    85
    Rand KR-2
    180
    Rans S-12
    60
    Rans S-6
    90
    Rans S-7
    118
    Rutan Long-EZ
    144
    Rutan Varieze
    165
    Searey
    92
    Sonex
    130
    Thorp T-18
    175
    Vans RV-10
    201
    Vans RV-3
    185
    Vans RV-4
    201
    Vans RV-6
    199
    Vans RV-7
    191
    Vans RV-8
    210
    Vans RV-9
    164
    Velocity
    230
    Zenair CH-601
    155
    Zenair CH-701
    85

    Ron Wanttaja

  2. #2
    DaleB's Avatar
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    Don't forget the RV-12 at roughly 135-ish MPH. I see 117 - 120 kt TAS in cruise if I'm not dawdling.
    Measure twice, cut once...
    scratch head, shrug, shim to fit.

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    Dana's Avatar
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    Hi, mid, low... what about biplanes?

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    Quote Originally Posted by rwanttaja View Post
    ... Below is my initial input to the analysis. I got them through a simple Google search. But I'm sure some folks here know better, and am interested in some feedback.
    Varieze:170 mph
    0-235 Long-EZ: 170 mph
    0-320 Long-EZ: 195 mph
    COZY III: 195 mph
    COZY MKIV:190 mph
    O-360 Berkut: 225 mph
    O-540 Berkut: 245 mph
    Velocity: - many variations - fixed gear will be slightly slower than a COZY MKIV, retracts will be slightly faster than the MKIV, and the XL versions will be faster than the MKIV, especially the TXL version. Can't really put only one # on it - it's like saying "Cessnas go this fast"...

    There's a fair amount of variation within populations, but these are pretty reasonable estimates for your garden variety canards.
    All mid wing.

    I also think you're substantially overestimating the RV speeds - the ones I've flown in (or next to) are not as fast as you're listing.

    Personally, I'd use kts rather than mph, but that's just me, and it's just a number on the x-axis :-).

    All my $0.02 :-).

  5. #5

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    Quote Originally Posted by Dana View Post
    Hi, mid, low... what about biplanes?
    Ron does crashes of airplanes.

    Biplanes are more than just airplanes, and so are above such pedestrian efforts as statistics.

    (7/8 scale Nieuport 11, 60 mph)
    The opinions and statements of this poster are largely based on facts and portray a possible version of the actual events.

  6. #6
    rwanttaja's Avatar
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    Quote Originally Posted by Dana View Post
    Hi, mid, low... what about biplanes?
    Hmmm....this is why I post questions like this, because other folks come up with investigation lines I haven't considered.

    My theory is that high-wing aircraft have more structure around the occupants' head and upper bodies, thus their fatality rate is lower. My results generally seem to bear this out.

    If it's correct, though, biplanes should be the safest.

    So...what are some common biplanes? The Pitts immediately comes to mind. There are 71 Pitts accidents in my 1998-2016 database. Note that these are Experimental Amateur-Built aircraft; I don't include the certified versions.

    I type "Pitts" into the search function, and it tells me the Pitts has a 21% fatality rate. This is better than the overall rate of 25%...but I really expected it to be better.

    I typed in "Christen Eagle", and was shocked: 37% fatality rate.

    What the hey....?

    Then I took a closer look at those fatal Christen Eagle accidents. There were 13 of them...and almost half of them (6) were due to maneuvering at low altitude. Low level acro, for the most part. Maneuvering at low altitude has an extremely high fatality rate.

    In addition, three MORE fatal Christen accidents fall into a category I call "Failure to Recover"...started a maneuver at a high enough altitude, but for some reason didn't recover before ground impact.

    So the Christen comparison isn't too fair...they have a lot of accidents in modes that most homebuilts don't operate in.

    Oddly enough, when I took a closer look at the Pitts, the number of cases of Maneuvering at Low Altitude/Failure to Recover were almost the same as the Christen...nine and three, respectively. Plus it had only two more fatals than the Christen. This is interesting, since the Pitts saw more than twice as many total accidents.

    BTW, both aircraft have a "Maneuvering at Low Altitude" rate more than three times higher than the general homebuilt population.

    Stardusters, on the other hand, have a fatality rate of about 15%, much lower than average. Only eight fatalities for 55 accidents, but half of them are Maneuvering at Low Altitude or failure to recover. However, one case was builder error, in that the elevator weld gave way during a low-level roll.

    Anyway, good thought, and I'll incorporate it into my analysis.

    Ron Wanttaja

  7. #7
    Dana's Avatar
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    Regarding Pitts vs. Christen, many Pitts's are homebuilt whereas the Christen is always factory built. As a result, the Christen will appeal more to the "I want it now" type of pilot with money who buys more airplane than he really should?

    Regarding Stardusters (Starduster One, 105mph cruise for mine at least), I can attest to its stoutness after my forced landing and subsequent cartwheel. The Stardusters are less intended for hardcore aerobatics than the Pitts or Christen, which may speak to the kind of accidents.

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    Forgive an 'uninformed' question. What is the definition of 'fatality rate"? Number of deaths vs number of flights? Number of deaths in any accident? Certain accidents?

    Just wondering. I'm presuming you feel there is a correlation between the location of the wing and general crash survivability? That would of course require comparing very similar crashes happening to machines with like mass/weight/velocity/impact angle etc? as well as wing location.

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    Quote Originally Posted by CHICAGORANDY View Post
    Forgive an 'uninformed' question. What is the definition of 'fatality rate"? Number of deaths vs number of flights? Number of deaths in any accident? Certain accidents?
    My definition of Fatality Rate is the number of accidents with at least one fatality, vs. the total number of accidents.

    Quote Originally Posted by CHICAGORANDY View Post
    Just wondering. I'm presuming you feel there is a correlation between the location of the wing and general crash survivability? That would of course require comparing very similar crashes happening to machines with like mass/weight/velocity/impact angle etc? as well as wing location.
    Certainly, but unfortunately, that's difficult data to extract. Plus, of course, accidents are random events...a fatality might depend on whether the passenger is leaning over to tie his shoe, etc.

    I certainly understand I can't *prove* the theory that wing position affects survivability. I'm attempting to find some correlation by using thousands of aircraft in each configuration. The homebuilt accident record provides about 3800 accidents over the 19-year period my database runs.

    Obviously, the speed at impact is a very big driver...energy increases by the square of the impact velocity. I'm hoping to use cruise speed to differentiate...but, of course, few airplanes actually CRASH at cruise speed. I'm using cruise speed just to indicate the approximate operating range of the aircraft. An RV-6 approaches faster than the cruise speed of Frank's Nieuport, but by using cruise speed as the factor the difference in capability is acknowledged.

    One drawback is that there ARE no quantities of high-performance high-wing homebuilts. There are a few Aerocomps, even fewer Stallions. So it's hard to get data in the higher-performance regime.

    There is some correlation in the production-aircraft world. The Cessna 172 has a fatality rate of 12.%, while the PA-28 (through the -181) it's 19%. The Bonanza and the Cirrus both have rates in the low '30s, while the Cessna 210 is 20%. However, the 210 has a lot of landing-gear-related and fuel starvation accidents, which usually aren't fatal.

    Ron Wanttaja

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    To get meaningful results you'll have to consider and group the class of accidents. As you say, some accidents are less likely to be fatal (a gear up landing, for example, or a forced landing in a rough field with no stall spin) regardless of the aircraft configuration. And there are other variables... conventional engine in front, vs. pusher (VariEZ) vs. pylon mounted engine (Searay, Kolb, etc.) might be significant. And many if not most of the "slippery" airplanes that pick up speed fast when things go wrong are low wing, whereas biplanes probably have the lion's share of accidents due to low altitude aerobatics.

    The thing with homebuilts, it's a pretty small statistical universe with wide variation. Looking at GA accidents might be more instructive, not only are there a lot more of them, but a Cessna 172 is, for example, pretty similar to a Cherokee 180 except for wing location.

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