Flap Malfunction in 172
 

Yesterday I was flying vfr and headed inbound to the airport, I proceeded to make a simulated fire emergency landing. I ran the checklist then I put twenty degrees of flaps in on downwind and then thirty on base. I noticed I was a little bit high, I slipped the airplane right and then heard a popping sound. The speed I put the flaps down was at normal flap operating speed. I looked over and the left flap was up and the right one was down. My first reaction when I heard the pop was something just broke, and then I saw what was going on. I was about 200 feet high and coming down to the threshold. I was thinking about putting the flaps up but then I decided not to because the airplane was still flying well. I made the landing and the cable to the left wing flap had broken. Any suggestions on configuring the airplane or leaving it like it was in the air?

I think the conventional wisdom with a flight control malfunction (flaps are secondary flight controls) is to follow the QRH/emergency procedure if your SOP or AFM provides one.

If no procedure is available and the airplane is controllable, don't change configuration and keep airspeed as constant as reasonably can. Avoid sudden power or A/S changes. You did the right thing...if you had tried to raise the flaps that loose cable might have gotten involved with something you really needed, like the aileron mechanism.

Well you were probably smart for leaving a flying airplane alone, if you had retracted flaps you would have encountered a high sink close to the ground, so you did the best thing. Squawk it to the club and count it as a learning experience. You'll get much worse in your flying career- smoke, fire, and losing an engine are far more exciting.

Thanks, I was thinking along the same lines about sinking down to fast, and if the airplane was still flying leave it alone.

Agree
 

The plane broke, and you were cognizant of it's handling capabilities (controllable). Who knows what would have happened if you raised the flaps.

Had a similar experience in an older 172 doing T/Gos and the flaps stayed at 40' on the go. I did raise them after landing per the checklist, which irked maint as they wanted to "see" the flap lever at 0 and the actual flaps at 40.

Slightly off the current topic, but care should be taken not to retract to less than a 20 flap setting on go-arounds in older Cessna singles with the 40 flap angle and no flap detents. That system allows a continuous flap retraction to a nose-high attitude which could easily lead to a stall. Flap retraction shifts the effective chord line up at the rear sending the tail down and the AoA up. Never go less than 20 until forward speed is regained to at least 55 knots (see POH).

I was a relatively new PPL at that time and knew that there were issues with 40' flaps in the older 172s - that's why they are now limited to 30'. I was somewhat uncomfortable (ok, scared) on that go around with 40' of flaps hanging out.

Good job landing safely. I'm amazed it was controllable with one flap at 30 and the other at 0. Was it trying to roll hard?

First, good job.

Was there a bunch of rolling caused by only having one flap?? I've always kinda wondered what the airplane would do and how bad it would be, and I've heard stories from other CFI's, who probably heard stories from other CFI's, about people getting split flap conditions and almost completely losing control.

Does anybody know if this has anything to do with why 172's are placarded with something along the lines of "slips with flaps should be avoided"?

Actually there wasn't to mcuh of a roll, I always thought if that happened it would make a roll. Maybe I was close enogh to the ground that ground effect helped out some, it felt like it was pulling some to the right on the flare but seemed like normal. It's an older 172 and I don't think that 40 flaps would be recommended even in a emergency with the stuff I've know read. What do you think?

I think slips should be avoided with 40 flaps, and if slips are done make the slips very gentle not rough.

I think at altitude it would present a problem?

IIRC, flaps 40 and a slip could block the airflow over the elevator, causing an abrupt drop of the nose. No bueno close to the ground.

I am gonna call myth-busters on this idea of a nose drop for these older Cessnas with the 40 flaps. I have never seen any proof of it. Tail blanking does occur, where turbulent or dead air causes light buffeting as the turbulent air from the flaps bumps around on the tail a little bit. But this is not the same as tail stall. It might be possible with some combination of conditions like forward CG, gross weight, crosswinds, and aggressive maneuvering, but I have never heard of any accidents from that cause.

That said, there are plenty of good reasons to avoid the 40 flaps on electric models. Go-arounds are difficult, there is a risk of wing stall due and mis-trim given complete flap retraction, and you can get extra drag for steep approaches by forward slipping. The older models with the jack bar were ok because you could change flap settings quickly on those models. Too bad they gave that feature up to get more interior room.

I can confirm the tail blanking in a 172N model with 40 degrees flap, definately an experience.

I had a right side flap cable break on a C310, but couldn't confirm until I was on the ground. I did however think initially it was an engine failure because of the rolling and no other changes, then as I was performing the 'recovery' it hit me what was happening, I retracted the flaps and she flew just fine.

Agreed. In fact, I seem to recall slipping with F40 was never a limitation, just a "not recommended" maneuver. The reason being that it would create buffeting. I did them many times with students, and never experienced a tail stall or anything abrupt like that. If that were even a possibility, it would be a very well known limitation.

Even the new cessna R and S models have that placard next to the flaps, and they only have 30 degrees of flaps

Agreed. You aren't supposed to slip for long with low gas in one tank, because you might run out of gas, but I've done lots and lots of approaches with 40 degrees flaps and slips. I can say that at least once I did feel what seemed like "tail buffeting", but per the relevant manual, there was no loss of control or other ill effects. If this was a limitation...well, it would be a limitation...