Is your plane trying to tell you that something is about to break?

There’s one way you can mitigate the renter’s problem of not knowing the airplane well enough – always fly (or at least try to fly) the same airplane(s). I used to do this when I was renting and to degree still do in our club. You get to know a couple of airplanes really well that way. Certainly not as intimately as an owner, but well enough that the airplane can actually talk to you.

I raised the gear on a rented C177RG Cardinal, it took a while to retract with a weird sound and the light did intermittent flash, something I just disregarded, the next flight front gear failed to retract and I could see it hanging halfway on the wing mirror, I did re-extend it manually and decided to fly it like a fixed gear slow C172 all the way from Exumas to Florida, turns out the extra drag from the gear is a non-issue: flying range does increase when one throttle back bellow to VLE compared to 75% cruise figure

Post maintenance revealed it was an issue with the front gear switch sensor, and not even sure it was fully retracted on my first attempt, I believe this was related “some big tug” used to tow the aircraft into the hangar when we were away, the aircraft owner thinks it was my crappy landings on a new type, a the end I paid for his pack of rum and he discounted his rental price

We have all been there with gear I guess. Brand new twin, not many hours on the clock, put the gear down, and all seemed well, but not a green light in sight. Of course some bu%%er had turned the rheostat so low that even in daylight the greens did appear, infact the rheostat actually turned off the lights alltogether. Not surprisngly it ended rather well, but with embarassment.

My plane had an odd problem for a long time that very occasionally the engine would lose power for a fraction of a second. It was really maybe 0.2S but it seriously got your attention! Nobody could ever find a reason. Then I changed to a different shop and among the many things the new shop decided were necessary was to change all the plug leads. The problem has never occurred since (about 8 years now). I still don’t really understand it.

I’ve also had the problem of starting with a flat battery and losing electrics. Everything was fine until I retracted the gear. Between the gear pump and the load into the flat battery, it was enough to trip a breaker somewhere. And now the battery was too flat to excite the alternator. First sign was that the TC flagged. Then I looked and realised everything was off. Luckily I already knew how to hand pump the gear, but I was on an IFR flight plan so tower wasn’t expecting me to return and land.

I confess I forgot to look for light signals. After I landed I called the tower by phone to explain (and hoped I wasn’t in trouble). I will never forget what the tower guy said: “We’re just glad we can still talk to you.”

John

johnh wrote:

Nobody could ever find a reason. Then I changed to a different shop and among the many things the new shop decided were necessary was to change all the plug leads

I had something similar a while back (except it happened for longer than 0.2 seconds). It always seemed to happen on humid days and went away after turning the carb heat on, so I had always put it down to carb icing. One day the aircraft failed a mag check, and we quickly found it was a failed spark plug lead. We’ve never had a recurrence – I replaced both sides of the harness (there must have been another intermittently faulty lead on the other mag for the engine to run rough at all). Once the failure was no longer intermittent it was easy to find which one it was – run it on the “bad mag” and find the cold cylinder, then start debugging from the spark plugs inwards till you find the culprit.

Popping sounds in my experience (on power reduction or changing the mixture) are almost always exhaust leaks. If you hear them, when the engine cools, check the exhaust system very carefully, and feel the parts you can’t see (I found a hole once the size of a pound coin where the exhaust curves under the engine after hearing popping on power reduction), and look around the flanges where the exhaust is attached to the cylinder – look for grey deposits on anything nearby. Also check things like EGT probes for grey deposits where they shouldn’t be.

If you keep repeatedly blowing gaskets on a particular cylinder, check that the mating faces are actually flat (on a plane I used to own, the mating face on the flange was not quite flat, and it blew two gaskets within about 30 hours), check that the studs are actually secure (last year, the Auster kept blowing exhaust gaskets – and when we took the exhaust off, the stud came out complete with helicoil, it wasn’t secure at all, and we ended up having to replace the cylinder in the end. I determined it was only torquing up correctly because the helicoil was being pulled up against the exhaust flange, so it would feel secure when you tightened the nut, but it wasn’t). Other indicators that all was not well was the CHT on this cylinder was unusually high compared to its opposite number, but it had always been that way since I’d owned the plane. The new cylinder tends to be within a few degrees of its opposite number in cruise, by contrast.

I would think that the exhaust failure would precede heat blisters which develop over time, and therefore should be detected during the annual. This also raises the question why exhaust manifold is not offered made of Inconel to avoid turning into blowtorch.

In our case it didn’t – we completely decowl the plane during the 6 month/50 hr check as well as at annual, and would have seen a defect then. The hole in ours appeared pretty rapidly.

Peter wrote:

they re-use just one small item from your old one; this tactic avoids them having to go through the expensive PMA process

And, in the spirit of Trigger’s broom / ship of Theseus, replace that small item at next repair ;-)