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Discussion in 'Aviation Mishaps' started by SepticTank, May 31, 2022.
Yeah, it was the stop & go I decided to stop doing.
I was just digging through some old picture files and came across an example of how careless mechanics can cause flap retraction failure.
This is the flap motor and jackscrew assembly from a 1970s Cessna single. It is sitting upside-down on the table. The motor drives a worm gear inside the gearbox, and turns the jackscrew. Inside the black collar on the tube are steel bearing balls that circulate and ride in the semicircular groove in the jackscrew. It's a low-friction device due to the ball-bearing effect. The flaps are supposed to be lowered all the way, to expose most of the screw, and the screw is supposed to get wiped clean at annuals or 100-hour inspections, and a bit of No. 10 non-paraffin oil applied to the screw. Just a bit.
But in this case some mechanic has been gooping it up with molybdenum disulfide grease, a lubricant specified for use on older non-ball, plain-thread jackscrews used in much older airplanes. Those affairs did not have the travel-limit microswitches on them. The service manuals specify different lubes and treatments for different serial number ranges of the various models, and if the mechanic can't be bothered to educate himself, this is what we get. Microswitches heavily contaminated with grease. Those switches are not sealed. At all. The grease gets into the and fouls their contacts and they quit working. Some mechanics know that it's supposed to get oil, not grease, but they squirt LPS on it, which then drips right onto the switches and gets into them. The service manuals specify wiping the oil on for good reason. All it takes is the thinnest film of oil.
That rectangular black thing with the two screws in it is the up-stop microswitch. It stops the motor when the flaps reach the fully retracted position. Now, if that switch's contacts are compromised, the flaps can extend, which closes the switch in preparation for retraction later on, but the switch will not conduct with all that crap in it and the flaps will not retract. Somebody on a T&G in a 150 could be in a lot of trouble. Even a 172, loaded to the max on a hot day, could be in trouble.
This is the down-stop switch. That grease finds its way out there, too. If it fails, the flaps won't extend. Remember that the jackscrew is upside-down in these pictures. The microswitches are UNDER the screw when it's in the airplane, and grease or oil drips onto them.
It takes hours to clean all that grease out of everything. Even the switches have to be washed out, or replaced. In this case, even the crimp terminals on the wires were full of grease and had to be replaced.
Then the whole thing has to be reinstalled and the switches rerigged to get the stop positions exactly right, and that job is horrible. The switches are on aluminum blocks on an aluminum rod, locked in place by tiny setscrews on the aft side of the blocks, where you cannot see them and you can barely get the tiny hex key wrench around there and into them. you're doing everything through an access hole well forward of this whole thing. With one hand. By feel. Which is why some mechanics just squirt oil on it, from a distance, rather than carefully apply just a bit. I put a bit of oil on a clean rag and wipe it on.
POS should be in jail.
With full flaps even a reduction of one notch in a 150 results in some sink. You have to go by increments and let the plane settle. If he went full flaps up I can imagine it becomes the scenario where you see the ground getting closer and just start yanking back on the yoke.
Thanks! I normally fly Pipers. My takeaway from this is that if I'm every flying a 150, 172 or similar, to not put myself in a position where my safety is dependent on having the flaps retract. Or in other words, no full flaps unless I know I'm on short final for a full stop landing. I say that in part because some people never use full flaps in those aircraft.
Isn't that taking it a bit far?
That's a maintenance screw up and you shouldn't be working around it. You shouldn't be flying with such a plane. If they do not follow correct procedure in one areas of maintenance they could also do that elsewhere, which leads to the end conclusion of "I'll make sure I don't use the engine unless I am going for a full stop fireball landing, because I don't trust the mech", which is very safe, it keeps you on the ground unless it's gusting like mad or you are.
In those aircraft? I don't think I'd be giving up anything. I say that because I don't see any additional risk, or any significant disadvantage actually, of not going full flaps until I'm committed to land. If, for whatever reason, I'm going to do a touch and go, then why not do that at flaps 25? All I'd be losing is a little bit of flexibility in being able to come in higher and go down steeper, and I could always slip to mostly make up for that. Seems like a non-issue. Where trying to go around w/ full flaps sounds like a PITA, at best.
Dan Thomas, that looks a bit familiar.
3 adult men in a 150 HP Cardinal, landing on a small private grass strip out in the boonies.
40 degrees of flaps made a nice landing, using 2/3rds of the runway. Selected full up, nothing happened. We flagged down a passing farmer on a tractor, and naturally he had a suitable screw driver.
I removed inspection covers until I found the one where I could see and feel the motor shaft. With our finger tips, we turned that shaft a quarter turn at a time for about 15 minutes, to get the flaps to zero. We left the screw driver stuck in the top of the specified fence post for the farmer to retrieve on his way home.
Our next stop was Tangier Island for lunch, slips only, no flaps, and the same when returning to the home field.
Failed micro switch. Almost certainly, from lubricant. I have replaced many similar micro switches, and most were contaminated with oil or greases.
I learned to fly in 150s and don't remember them being unable to climb with full flaps. Slowly, yes, and you had to retract them v-e-r-y slowly on a go-around, but it would climb. But I was probably 140# then and my instructor wasn't a big guy, either.
When the 152 came out a lot of people were upset that they only had 30° and there was a letter writing campaign to Cessna to change it... but the story was that despite the slightly higher HP the increased prop rpm made for worse climb than the 150, so they had to restrict the flaps to meet the FAA required climb performance.
Of course all that was 45 years ago so I could well be misremembering.
It’s all about density altitude, push that high enough on a hot day and you won’t be climbing in a 150 with full flaps even if you’re a 75 lb pilot.
In the situation I had, I was about 170 lbs, my student bigger yet, and outside air was over 90 degrees.
I recall doing dozens and dozens of T&G's and go-arounds in a 152 before getting signed off to solo. Over and over, 15 or 20 in a row in a nice tight pattern, until it was an automatic reflex action. Full power, carb heat off, flaps out one notch at a time.
Banning T&G's is insanity. A crash on rollout 99% of the time results in bent metal and minor injuries. A stall spin on departure 99% of the time results in death.
30 years later I still do at least one T&G every time I fly my Decathlon for aerobatics, which can be 3 or 4 times a week. I usually do both a wheel landing and a 3 point landing to remain equally proficient at both methods.
We're talking about AFTER solo. And the above is not the right procedure for balked landing even. You need to get the flaps up to 20 IMMEDIATELY after jamming the knobs forward. If you're on the ground (as in T&G), you'd be advised to retract them to the takeoff setting before advancing the power.
Yes, and if you have a good CFI who makes 100% sure you are competent in T&G landings BEFORE you solo, then you will not have a problem AFTER you solo. Whereas if you have a crappy instructor who "cleans it up for you", then you better hope nothing goes wrong while you learn on your own. Capice?
Fair enough, I started my training in the fall and finished in the spring, didn't do much 150 flying in the summer heat.
When I learned it was all touch and goes, including my first solos. My tipoff when it was time to solo was when the instructor took the mike on downwind (no headsets back then), said something to the tower I didn't hear, and they cleared me for a "stop and go." But it was a 5400' runway.
Nowadays, I do a lot of landings just for fun, but almost always full stop... but I'm usually landing on a 900' bit of grass alongside the paved runway. And, of course, in a taildragger landings only count for currency if they're full stop.
I understand just fine, but if your instructor drilled into the WRONG way to do t&gs it's not any better than mine never teaching me the right way.
I’ve soloed about 25 students, half in a 150. We did touch n gos. I didn’t get out of the plane until I was 100% confident in their success. I didn’t sit with a walkie talkie, since I didn’t get out without complete confidence. In most cases they flew better without me in there. And some went around as needed.
That post reminds me of a discovery I made about the microswitches used to sense landing gear position on the Piper Arrow. The switches are not unlike the ones pictured in the example above -- they are not sealed, and not waterproof. On the Arrow, they are exposed to weather with gear down, and if you fly in rain, they are going to get wet and will eventually fail.
For me, the result was three green lights, plus the red Gear Unsafe light all illuminated at the same time. Turned out the gear was in fact down and locked so the landing was fine, and I got to wave at the guys in the fire truck on the taxiway. Bottom line though, is that there are some things the engineers overlooked in the design of that airplane.
On my solo (172) my cfi may or may not have had a walkie. If he did I didn’t hear a peep. But I did at least 3 satisfactory landings before he let me loose that day.
I almost always do at least one T&G after acro practice, because I try to do an equal number of wheel and 3 point landings. So l usually wheel land for a T&G followed by 3 pointer for full stop.
I’d suggest doing it the other way once in a while, too.
I do that too. My hangar is off the west end of the runway. If landing 90, I wheel land for a T&G, then do a short field 3 pointer to minimize back taxi time. If landing 270, I do a 3 point T&G, then a wheel landing and taxi to the end with the tail up.
Every flight for me is a new learning experience , only 130 plus hours but well over 400 landings . One memorable touch and go when I forgot to raise flaps was really interesting. My straight tail 172 has Horton STOL kit and will climb with 30 degree flaps but never exceed 70 MPH and not climb very fast on a warmer day .
Full throttle , mixture full rich , carb heat off , why is it not climbing like it should ?
A few moments of puckering as the runway slid past me ,before remembering to slowly lower the Johnson Bar.
I now work in aviation safety, and it has been... Illuminating.
It is NOT about eliminating all risk, because aviation and life itself have risk. Period.
It IS about mitigating risk and deciding what an acceptable level of risk is.
For example - I used to be based at the field where this accident occurred. The runway it happened on is 3200 feet IIRC... Not a heck of a lot of room for error or even executing the steps slowly for a T&G. However, I did my flight training at an airport where the shortest runway was 5800 feet, so I had all the time in the world. It makes perfect sense to restrict T&Gs at one and allow them at the other.
This school not allowing T&Gs on solo but allowing them in dual instruction and allowing the instructor do the cleanup is problematic from a human factors perspective. It's fine if every student obeys the "No T&G" rule and never does touch and goes in the future, but it's not great - And with this student exhibiting some hazardous attitudes, there's two of the proverbial swiss cheese holes lining up.
FWIW, I'm hoping to someday put together a presentation based on what I've learned about aviation safety and how it can apply to single pilot GA flying, because there seems to be this misconception that safe and fun are at odds with each other. That's where attitudes like @Salty's and @Whitney's come from - But it is perfectly possible to be safe AND have fun... And having an accident is most certainly not fun either.
I agree with you that student pilots should not do touch & goes during a solo. However, T&G are a great training tool during dual. Unless you are flying a retract or are at a super short field T&G lets you learn landings and go-arounds at the same time. A new solo student might have, what, a couple of dozen landings and may be one or two go-arounds. That much of go-around experience is simply not enough to handle a real situation.
Nope, you got me wrong.
1. I agree that 3200 feet is too short for a student to do tngs on. My comment was on the flat statement that students shouldn’t do tngs period.
2. There’s no magic in passing a checkride that makes tngs suddenly safe. Again, my comment was directed to the blanket statement that students should not do tngs.
My comments on this thread have been more about the idiocy of blanket restrictions like “students should not be allowed to do tngs” than it is about the safety or fun of doing tngs. I wouldn’t do them in my Mooney at my home airport (3700 feet). But I would at the 10,000 foot airport close by. I would also do them in the skycatcher at my home airport. It all depends on many factors.
Day one of pattern work should be nothing but go arounds. That default skill must be taught. IMHO
Well, not nothing but go-arounds. At least, I hope you allow for one full stop before the tanks are empty.
Prelim out, likely nothing wrong with the plane, yes tragic.
A good CFI should be best positioned to know whether or not a given student will benefit from touch and go practice solo, or needs a no touch and go restriction. It seems very problematic to repeatedly have a CFI perform any task for a student- retracting flaps, adding rudder, whatever. Occasionally, or for demo purposes, sure. But IMO cfi should be calling it out so that student is aware of the action.
only a 400 hr pilot here-but I do touch and gos regularly in moderate crosswinds- for me, it’s good practice. Stop and go’s or taxi backs for night landing currency.
I’m not sure restrictions on t&gs help pilots stay proficient. As others point out- what may be sensible for a short field may not be needed at a longer one.
Such a sad loss. Reminds me of a time it could have easily happened to me.
I was renting a Cessna 152. Almost all of my time up to then had been in Pipers with the Johnson bar. I was practicing T&Gs in the Cessna 152 and on the first one forgot to retract the flaps. I never realized my mistake until I wasn't climbing and almost out of runway. Unfortunately, when I went to push the flap switch up with my right index finger, I accidentally bumped it all the way up to 0 deg. I immediately felt the airplane start to settle and knew I was in a tight spot. My mind was tempted to fixate on my mistake and push the flap switch back down to 20 degrees. However, I forced myself to look up and out and pushed the yoke forward. I recovered at about 20 feet and started climbing again. Pushing forward is what allowed me to climb which is something new pilots don't always fully grasp. Your elevator doesn't control your "elevation," it controls your angle of attack / speed.
Looking back, if I had been a newer pilot, as soon as the airplane started to settle (horrible feeling for a new pilot) I could have easily panicked and pulled back on the yoke. Even if I didn't panic, I probably would have decided to "fix" my mistake. I would have looked back down at the flap switch on the lower instrument panel, and much more carefully and deliberately moved that flap switch back down to 20 degrees. Meanwhile, while fixating on the flap switch, I would have been pulling further back on the yoke without realizing as I maintained constant pressure on the yoke (airspeed dropping), and I would have stalled.
I think every student pilot should practice T&Gs before soloing and should be allowed to do them. Otherwise, if they bounce on landing, they're likely to be confused as to what to do next. "I already touched and I'm not allowed to go, so I guess I'll just porpoise and collapse the nose gear instead".