Pushing down on the Elevator

[Mtns2Skies]

I have heard both sides to this, Is pushing down on the horizontal stab an acceptable method to moving an aircraft? I have seen CFI's do it and I have had CFI's tell me not to do it. Obviously only pushing on the inboard bit... but is this advisable or does it cause damage? (Tricycle gear only)

[Bill Greenwood]

I don't know for sure, and I haven't read anywhere in any plane manual about this, like you do read prohibitions against moving one by pushing on the prop spinner. It doesn't look like the best practice, better to get a bar to attach to the nosewheel to move it.
I have often seen CFIs move a small Cessna by pushing down on the tail to raise the nosewheel off the ground so they can pivot the plane around. I think I have also seen gliders moved by pushing down on the nose to raise the tail wheel off the ground.

But if you think about it, it probably doesn't really do harm, we don't see airplanes crashing very often because the hor stab fell off after being moved like this.
Think about it, a standard Cessna 152 is built to stand 3.8 gs, I believe, some planes like some Beechs more than that, not counting acro or military planes.

So the stab can stand 3.8 gs, and when you push down you are not applying anywhere near that, maybe a 200 lbs man might push down 60 lbs. of force. You are not having Shaq jump up and down on the stab.

[seeekandstroy]

Any time I push down in the back, it's on the stabilizer, not the elevator. With that said, I had to do that only once to get the nose out of mud. If you do push down, lift the nose only as far as you need it, usually only an inch.

[Floatsflyer]

From day one, my instructors taught me to push down on the dorsal fin only(for 150/152 & 172), never the stab. I haven't been concerned about this technique for years as the 182 I fly has retractable handles at the rear.

[Mtns2Skies]

...the 182 I fly has retractable handles at the rear.
First off... that is REALLY cool!

Second I was purely curious because I have gotten so much conflicting information on this... but it doesn't matter that much to me. The planes I fly have the wheel in the correct place, In back! :D

[WLIU]

The preferred method on a Cessna is to push down on the fuselage. That said, pilots have been pushing down on the inboard end of the horizontal stab for years. It is best to push on the rivet line for the rib and the forward spar.

The engineers know that pilots push the airplanes around in that way. Ground handling loads are part of the design calculations. That said, most older Cessna's, particularly 182's, 180's, and 185's wind up with broken inboard nose ribs in the horizontal stab. When a smart mechanic does the repair, he or she beefs it up a little. But that only happens if there is a reason to take the skin off. Mine got beefed up when I got some hail damage and had the horizontal stab reskinned.

The retractable handles for pushing the airplane around are a great idea and good investment.

Best of luck,

Wes
N6234A

[martymayes]

I have heard both sides to this, Is pushing down on the horizontal stab an acceptable method to moving an aircraft? I have seen CFI's do it and I have had CFI's tell me not to do it. Obviously only pushing on the inboard bit... but is this advisable or does it cause damage? (Tricycle gear only)

A CFI probably isn't the best resource.....


Ref: Cessna Mandatory Service Bulletin No. SEB94-8 released April 29, 1994.

"NOTE: Improper ground handling can cause cracking and deformation of the horizontal stabilizer structure. It is recommended that a tow/steering bar be used whenever the airplane is to be manually positioned on the ground. Do not steer the airplane by pushing down on the horizontal stabilizer.”

In addition, the Cessna service manual for 100-200 series airplanes states: “Caution: do not push on control surfaces or outboard empennage surfaces.” (that means in any direction)

Cessna's S.E. safety initiative re-emphasizes not to weight, push or lift on the horizontal stab. One engineer at Cessna said the majority of field report cracks were traced to pushing down on the stab.



Not sure how to make it any clearer.

[Victor Bravo]

It is also very important to note that these airplanes were never designed to be in service for 40-60 years. They were originally designed to be flown by the owner for seven or eight years, and then traded in for a new one just like a car. THAT is why most airplanes do not have nearly enough inspection access panels, and why it is so difficult to do anything other than short-term routine maintenance. The original designers of Cessna, Piper, and other types of aircraft would be turning in their graves if they knew their airplanes would stillbe out there flogging along 50 years afterward. They would have made many many different decisions, and put in much more access panels, and done a lot more corrosion protection.

There is also the simple fact that you are asking a 30 or 50 year old airplane to protect you, protect your family, and give you a safe flying machine. Anything you do that risks un-necessary damage is just not smart. When was the last time the stabilizer has been off of that aircraft for inspection? Chances are, it has never been off since it left the factory at Wichita. Even when wings are removed, many times the tails stay on.

IMHO Pushing down on the stabilizer spar at the root with 50 or 80 pounds of force is reasonably harmless. Yes it was designed for a lot more force than that. But pushing down on the unsupported leading edge of the stabilizer forward of the spar is just stupid, it damages the airplane, and is an immediate indication of someone who should really not be around an airplane.

Anyone who lifts or pushes a light airplane around by the spiinner is an idiot, and should be taken out behind the hangar and beaten. I have personally had a spinner come off in flight, it took off part of a propeller blade, and I had to shut the engine off inflight to avoid having it fall off of the airplane. NEVER put any force on the spinner! It is designed to be loaded only very lightly, and any misalignment or stretching can cause a vibration that WILL get serious very soon.

[Joe LaMantia]

Well said, Victor Bravo!

My instructor used the centerline of the fuselage just forward of the tail fin to move a C-150 around in tight circumstances. He pointed out that the leading edge of the horizontal stabilizer should not be used and that Cessna had some advisories regarding tail inspections on some models. We always checked-out the rivets and general condition of the skins on the horizontal stab. That pre-flight inspection has stayed with me to this day. As for the spinner, if you take a look at how they are attached and what they're made of, you can see that using them to push anything more that air would be a mistake.

Joe
:cool:

[FlyingRon]

Yes, on a 150 and even a 172, it's easy to stand with your back to the horizontal stab and put your arm over the top of the fuselage tube with one hand on the the root of each horizontal stab and press uniformly down centered on your armpit enough to lift the nose and turn the aircraft. Once the aircraft is pointed in the right direction, I push on more solid parts (the wing struts).

On the Navion, I put my foot on the little skid piece that guards the rear tiedown ring enough to lift the nose (it's a lot heavier than a 152). You can then sort of hop the plane around with the nose gear off the ground.

[Mike M]

A CFI probably isn't the best resource.....

A CFI who says "READ THE MANUFACTURER'S INSTRUCTIONS!" is a wonderful resource. Seldom incorrect. Great advice, Marty.

[Mtns2Skies]

Okay well now that this is cleared up... How about pushing/pulling on the prop? I have never had any inclination to push on the spinner, but inboard on the prop?

[seeekandstroy]

I suggest not doing that. I've seen props broken at the hub from someone pulling from it. Sadly, the blade slipped out of the person's hand and hit me. Not fun.

[Bill Greenwood]

I think most prop manufacturers advise not to move the plane by pulling or pushing on the prop.

However, again, common sense would tell you that the prop is not that fragile. After all, it has to be strong enough to pull the entire airplane down the runway and through the air. which takes a lot more force than a pilot is going to put on it with a simple pull. Of course when the engine is running you have the oil pressure in the hub if it is a constant speed prop and that may stabilize the blades also.

If you have two people, one can easily steer the plane with the factory tow bar on the nosewheel while the other pushes on the leading edge of the wing.
If there is only one person you may have to steer the plane with one hand and push with the other. If it moves easily that may be fine,but if a lot of force is involved I would prefer to push equally on both blades or opposite blades of the prop near the hub.

[Mike M]

Okay well now that this is cleared up... How about pushing/pulling on the prop? I have never had any inclination to push on the spinner, but inboard on the prop?


Did you read the aircraft manual? The propeller manual? For example, Sensenich website has a sentence in the "continuing airworthiness" instructions, "Do not use the propeller as a towbar to move your aircraft." Pretty clear, but you may be operating another brand. I recommend you either do not do it or ask their customer support staff if you cannot find the answer in the manual.

[nrpetersen]

I'd infinitely rather push on a fixed pitch propeller near the blade root than on the leading edge of a low wing. Common sense should indicate that a fixed pitch prop structure is not going to be overstressed (in operation props are radially stressed to ~20,000 psi), and the supporting crankshaft etc is certainly able to withstand the moment of reasonable hand force.

Maybe there is actually a reason for variable pitch props, but it also seems hard to believe. Does anybody know why?

[Victor Bravo]

Because line boys and airpalne owners and even many licensed mechanics these days don't CARE enough about airplanes to be gentle with them. Some bonehead will try to pull the plane forward or rearward by grabbing the tips of the prop blades.

[Joe LaMantia]

On a level surface you really don't need a lot of leverage to move most single engine aircraft, and the tow bar works well. I have had the misfortune of having all of my club airplanes with slight uphill grades when returning to the hanger. Always easy to get them out of the hanger and go flying, but can be "work" putting them away when solo. The worst is winter when hard packed snow or ice form on the apron slope and you can't get a foothold when trying to put them back in the hanger. Several times I've had to find a rope or even an extension cord and tie it to the tail tied-down fitting and them pull them into the hanger tail first. The footing inside the hanger is always good. Take care to go slow and chock a wheel while you adjust the nose wheel or you can wind-up on some strange angle when the wings approach the door. I will confess that I have pushed on a the prop at the root while using the other hand to steer the tow bar. These have all been fixed pitch props, which start out as forgings that are very stout at the root, the tip would isn't a good idea.
I don't have any idea regarding the constant speed prop, but I wouldn't mess with one without getting checked-out.

Joe
:cool:

[Mike M]

http://www.mccauley.textron.com/von_klip_tip_10_commandments_of_prop_care.pdf

OK, the written info from Sensenich was beyond some folks' reading comprehension level. Google search for "mccauley ten commandments of propeller care.". They put it in cartoon form. If you STILL do not understand, contact customer service for the company that made your propeller. Please.

[WLIU]

I will suggest that many manufacturer instructions have a slant to them that is required by the legal department that makes them say "treat our product exactly as we say so that we do not have any liability for misuse". This falls apart upon contact with the real world. I doubt any readers of this forum have followed every instruction to the letter 100% of the time.

As Bill noted, if the propeller is strong enough to pull the airplane through the air, it is not going to be damaged by you or I pushing on the blade root.

The application of common sense in these issues is advised.

On the topic of pushing an airplane using the horizontal stab, while I will counsel care, I do have direct experience with how much impact a Cessna horizontal stab can tolerate. If you have seen a bird strike on a horizontal stab, or have seen your local skydiving center have a parachute open into a horizontal stab in flight, you will agree that they are more rugged than they look. They are not made of tissue paper. But try to avoid experiencing these events at home.

Fly safe,

Wes
N78PS

[Kiwi ZK-CKE]

Back when I was doing my aprenticeship as an aircraft tradesman, I was taught the way to push down the tail of a Cessna or Piper was to push on a rear fuselage frame. On a cessna it is the one at the base of the fin where the forward fin attachment is - All nosewheel cessnas have a removeable inspection panel between the fin and tailplane, and this frame is where the front edge of that panel is fastened. this frame is a machined item and is incredibly strong. Its a simple case of reaching over then fin and pushing with one hand on each side on that frame. Although using a towbar is the preferred method of ground handling, the nosewheel angles really arent tight enough when stacking aircraft into a tight hangar, so pushing down the tail is inevitable. The other reason for doing it is to access the nose gear for servicing. Many engineers will hold the nose in the air by putting a weight on the tailplane. the key thing is to avoid point loading - We protected the tailplane with a piece of carpet, then laid a piece of plywood so it would go over both spars as close in against the fuselage as possible. we then put some weights on the ply to keep the tail down - making sure they were stable and wouldn't fall off. Tieing the tail down is a better option, but not always practical - you often cant get the nosewheel high enough once the tiedown length is taken into account. Tailplanes take that downward load (and more) in flight, but the difference is the point loading.