Question for pilots

[Flipperk]

When i was in flight school awhile back my instructor was with me doing preflight, when we got back to check the elevators, he started pushing down on the horizontal stab. and it started to lift up the nose of the plane (Cessna 172S). I asked why he did that he said that if the tail section couldnt handle that, then there would be no way it could handle regular flight. A few months afterward i got a new instructor and I told him about what the last guy did and he told me that I should not ever do that because it causes unneccessary stress on the airframe, and also that the guy was full of cow poop.

The first instructor made sense and so did the second, which one is correct?

[Talon07]

Hmmm I'm a glider pilot but I'm employed in the aviation industry. It would depend how hard the 1st instructor was pushing down on the stab. A small amount of pressure to feel for play in the stab would be acceptable but as far as jumping and putting all his weight on it the second instructor is correct in that regard.
Kind Regards FBClaw

[Golfer]

I can't reach the elevator or horizontal stab on my airplane.  Hasn't fallen off yet.

And I've never ever seen anyone do what you describe and if I were I'd be inclined to laugh at them.  Quietly at first and if their behavior persisted very likely out loud and in their presence.  Now you do want to check to make sure the counterweights are there (should be 3 on each side) in the base of the ailerons outboard toward the wingtips.  Look up at them in the gap when the respective aileron is deflected upward.  That's about all I remember from preflighting a 172.

[Captfish]

I used to do it all the time with a 152 to turn it around, push on the tail and pop the nose up and spin! It never fell off on me, the first guy was right if it cant handle that then it will never handle the stresses of flight. Now with my Husky, a tail dragger,  I do the opposite, pick up the tail, and push the plane around, Aviat even installed a handle to make it easier.

[Cougar68]

The problem is that it's not an even force.  When the relative wind pushes on a control surface the force is spread out across the entire surface evenly.  To grab one end of the elevator and lift it also puts a twisting motion on the hinge that it wasn't designed to handle.  Probably not going to make anything fall off, but I still prefer to not stress an airframe in ways it wasn't designed to handle, lest it rises up in flight and smites me. 

[Maverick]

Pushing down on the tail feathers tends to put unnecessary stress on the internal ribs. That causes them to buckle and weaken the structure where you cannot see it without a detailed inspection through the inspection access panels. Same for pushing down on the fuselage, they are not weight bearing surfaces. The structure has a purpose and laying down on them is not it. In addition to buckling the support structure you also place considerable stress on the rivets and other fasteners.

If you want to check the tail, grasp the fore and aft portion and gently rock them back and forth to look for looseness or play in the horizontal stabilizer. A gentle up and down pressure in the same manner may indicate buckling of the structure as well but may also be caused by frequent stressing of the structure by ham handed pilots who have no freaking clue as to what they are doing by yanking, twisting the frame or jumping up onto the structure with parts of their anatomy.

Instead of making like you think you know something about the underlying structure, look for fretting rivets, loose screws, buckles in the skin or dents. Some of those dents may be inflicted by pilots messing with something they don't know about instead of asking.

[Roundeye]

In 20 years of working on and flying Cessnas, I have never seen a horizontal stab fail from this.  It is common to ground handle one by lightly "sitting" on the stablilizer close to the root to spin the plane around for parking and movement (like captfish posted).  Not exactly endorsed by Cessna, this is done on a daily basis at airports around the world.

Older 150 models did have a bulkhead crack problem related to this, but they should have all been updated by now.  One of my jobs was at an Authorized Cessna Service Center and even there, I never saw a defective stabilizer or attach point.

You would be hard-pressed to find an accident involving a single engine Cessna caused by structural failure due to design weakness.  Anything can fail from abuse or lack of maintenance, but Cessnas are about as tough as they come in general aviation.  There are plenty of faster and sexier planes out there, but few can stand up to the tests of time and punishment that Cessnas have endured.

[eagl]

The problem is that it's not an even force.  When the relative wind pushes on a control surface the force is spread out across the entire surface evenly.  To grab one end of the elevator and lift it also puts a twisting motion on the hinge that it wasn't designed to handle.  Probably not going to make anything fall off, but I still prefer to not stress an airframe in ways it wasn't designed to handle, lest it rises up in flight and smites me. 

QFT.  Exactly right.  Pushing hard on any one spot on an airplane could cause damage if you don't know exactly what you're doing.

[Casca]

It is quite common to handle Cessna 150/152/172 airplanes by pushing down on the tail and I don't think it presents a problem if done by pushing down as far inboard as you can at the spar.  The force involved is not very large.

[Golfer]

Like Casca mentioned you can move it around and manipulate it on the ground as long as you're pushing inboard on the spar and only the spar.  Pushing willy nilly on the tail section or worse yet the elevators is a great way to cause damage to the airplane you didn't intend.

[Grayeagle]

Gently rocking the flight control surfaces to check hinge/rigging play is a good idea, especially if you've never flown that plane before.
(we hates elevator flutter on fast descent to airport area
(or .. buzzing the runway 'the pattern is full Ghost Rider'

As for turning em .. near the root, directly over the main spar, have at it.
Anywhere else will cause problems.

-GE aka Frank