C172 pilots and CFIs

[SunDog]

Hello all,

Looking for some more C172 scoop from the bad-dream, bad-day Cessna universe. . .

Have you experienced a flap asymmetry in a C172, and will you share your narrative? I have some folks from other sources who have contributed (one was a T-41, which is pretty close to a C172) but would be grateful for additional insights.

Also, do you have a technique / procedure for flying an approach using trim-only for pitch control, through the flare and touch down? I'm particularly interested in your throttle/power manipulation just before the flare, flap setting, AS,  handling gound effect, and, of course, rolling in trim to flare. If you have tips, tricks, or tried a variation that didn't work so well, that would help to hear about, too.

To save some angst and time:
I'm very familiar with T-41s, know the flap limit speeds for a C172, and do check the flap attach rivets and flap play during pre-flight. And know to take care not to bang the nose -wheel.

And most Definitley NOT asking anyone to go experiment with trim-only landings - doing that myself - just looking to hear from the broader, experinced pilot pool about lessons learned and techniques devloped over time.

[Cliff_Chambliss]

Had a flap attach bracket fail on a 172 which resulted in the flap jamming the aileron. Flaps were jammed, ailerons were jammed.  Maintained control with rudder lots of rudder and landed. 
Flap bracket failure resulted from cracks in the rear wing spar to which the bracket was attached.  Airframe had in excess of 9000 hours.  Further inspection of the fleet found cracks in the rear wing spars of 7 of the aero club aircraft.  All cracks between rivet holes attaching flap brackets to the wing spar.  Not detectable during normal pre-flight checks.  Need to remove the fuel tanks or use a borescope to find.   Best we could determine is flaps were extended at too high an airspeed too many times.

[SunDog]

Grim. Glad you had the skill and calm to get it down safe. . .

May I ask, were the ailerons neutral when jammed? And did the flaps get very far? Ten percent? Maybe more? Did the motor keep driving, or did a breaker pop?

As an aside, I've been adding flap when NOT in a turn and with ailerons neutral,  like after rolling out level on base, for example.  Some of our aircraft have high hours, especially the T41s.  I've found rivets popped on flap attach brackets twice over the years, on the bottom row. Tough to see them in bright light, and if the anti-corrosion glop has gummed them up with dirt and dust.

Thnks again, much appreciated.

[a2capt]

I've had the flap jam on my 172N, at about the 30% distance, and it retracted to somewhere near 20% but at a canted angle, with the inboard edge pushing into the rear window, and mounting horn became pushed into the flap and the rod broke through.

Aileron movement was not restricted. The landing was a bit like a prolonged side slip with corrections added.

Several years later, another 172N had a very similar failure, it's tail # is "5 younger", I should look up the airframe serial #'s to see exactly how far they are apart, I do remember them being close, and probably "on the ramp" at the same time.

I may even have photos someplace. I'll see what I can find.

As a side note, thats's when I figured out just how big the flap really is.

It barely fit inside of a 1958 Dodge, when I went to get the replacement from an aircraft "junkyard".

[Cliff_Chambliss]

Grim. Glad you had the skill and calm to get it down safe. . .

May I ask, were the ailerons neutral when jammed? And did the flaps get very far? Ten percent? Maybe more? Did the motor keep driving, or did a breaker pop?

As an aside, I've been adding flap when NOT in a turn and with ailerons neutral,  like after rolling out level on base, for example.  Some of our aircraft have high hours, especially the T41s.  I've found rivets popped on flap attach brackets twice over the years, on the bottom row. Tough to see them in bright light, and if the anti-corrosion glop has gummed them up with dirt and dust.

Thnks again, much appreciated.

It was 2004 when this happened and some of the details are lost to the fog of age.  it was an instructional flight  but I really can't remember if flaps were being extended while turning jamming the aileron or if the aileron was jammed into the already extended flap.  I do remember it took a lot of rudder the keep the plane pointed in the right direction.

[SunDog]

a2capt, photos would be great, thanks. Digging into some much more active forums, I've found quite a bit on flap issues with C172s.  There is a lot of room to improve/create sim scenarios for flap failures.

The good news is, the failure modes seem survivable - the airplane has plenty of rudder (see Cliff_Chambliss post here). Also, the failures seem roughly split between jamming and not jamming the ailerons. Found some other folks who adopted the technique I mentioned, deploying flaps only when straight and level, ailerons neutral.

IRT my posts with questions about spin behaviour and positive G manuvers, the advice I got concerning the Cessna publications seems consistent with people's experience with spins - they apparently progress like Cessna says, as has been my experience with spins of less than three turns or so. And though there is very little margin for error in technique, and even less margin in structural strength, anecdotal reports confirm that the popular sims fairly accuratley depict a C172's behaviour in a SUCCESFUL loop.

[starshippe]

   not trying to hijack ur thread, just a couple of questions. the t41b is also a favorite of mine.
   do u have access to a t41b?
   if so, would u pls check the wt and bal and see if the calculated cg moved forward with the installation of the lighter engine, when it came out of mil service?

thanks,
bill

[RTFB]

These stories are good examples supporting the old rule of thumb never to extend flaps while turning, which most people (including myself on occasion, I am ashamed to admit) fail to heed.  If you get an asymmetrical extension, or heaven forbid interference with the ailerons, your chances of recognizing and coping with the situation before stall/spin/loss of control are much better.  Especially considering the altitude AGL when flaps are usually operated.  In a T-41 with 40 degrees of flaps, this could quickly be disastrous.

I've played around with simulated control failures in a 152, where both doors are more easily manipulated by a single pilot.  I also once flew with a great CAP CFI out of Chicago who demonstrated a full flight, from takeoff to landing, using only trim, power, and rudder in a 172.  A great learning experience I've been meaning to practice myself one of these days.  (This is why I love flying with as many different pilots/CFIs as possible- you always get something new.)  Unfortunately, I mostly fly 182s and don't have regular access to a 172.  I don't want to mess with this technique in a 182 until and unless I am thoroughly comfortable with it.

Kudos to those who handled these emergencies with skill and judgment.

[Critical AOA]

There was a good article in one of the aviation magazines (last year I think) that advocated doing that type of training with a CFI; flying the pattern using just the elevator trim and power for pitch / airspeed and the rudder for directional control.  No hands on the yoke. I have been wanting to do it but have yet to get around to it. I have tried it by myself away from the pattern at altitude and did okay but would want a CFI with me before trying to land that way for the first time.

[Cliff_Chambliss]

When you do this you will quickly gain an appreciation of just how effective the trim is. 

NOTE:  while you can fly using trim and power, be aware that as you near the ground you are going to have to be very fast on the trim to prevent the nose from pitching down as you get deep into ground effect.

How much power to use?  Here is a useful rule of thumb.

With the aircraft trimmed for straight and level flight:  changing power by 100 RPM if you hold altitude your airspeed will change by approximately 5 Kts.  Also, if you maintain airspeed your altitude will change by approximately 100 FPM.   These are approximate, but gives a place to start.

At altitude. With no power, full nose up trim let go of the yoke and the aircraft will stabilize at the best glide speed. 

[SunDog]

   not trying to hijack ur thread, just a couple of questions. the t41b is also a favorite of mine.
   do u have access to a t41b?
   if so, would u pls check the wt and bal and see if the calculated cg moved forward with the installation of the lighter engine, when it came out of mil service?

thanks,
bill

No problem, would like to assist, but we fly the T41C, 210 HP, with a fixed pitch "climb" prop, and that's how they came to us, I believe, straight from tbe Air Force Academy. Actually, I think they may still belong to the Air Force.  The climb angle on a short field take-off is impressive. . .my assumtion is the T41C came from Cessna with the 210 HP, with no STC like we have for the 180 HP C-172s in CAP.

The Fort Meade Club web site, http://www.fmfa.org/ , has a W&B spreadsheet for the aicraft. N7876N is an active T41C, at FMFA. Didva lot of my instrument rating in that airplane.