Loss of control involving Cessna 152

[djpil]

Loss of control involving Cessna 152, VH-JIW, 34 km east-south-east of Archerfield Airport, Queensland, on 28 May 2019 (https://www.atsb.gov.au/publications/investigation_reports/2019/aair/ao-2019-028/)
Seems to me there that they should've taken a look at instructor training here.

The ATSB stated that the "significant structural damage to the right horizontal stabiliser, which was indicative of in-flight overload during dive recovery". The pictures show buckling on the top surface so it seems to me that the damage was indicative of loads prior to recovering from the dive. My reference is SAE Paper 700222, Loading Conditions Measured During Aerobatic Maneuvers.

It also demonstrates that bits other than the wing can fail first and emphasises the importance of rolling G.

[Whopity]

What has been done as a resultThe operator has revised its training procedures for use of trim to include detailed instructor demonstrations prior to the student practicing manoeuvres

Clearly they had never heard of Demonstrate; Teach; Practice!

[DCS99]

The photos in the report. Wow!

[sandringham1]

From the way the tailplane has distorted it was obviously subjected to huge forces and yet they state there was no evidence of damage to the attachment points, or whether the rear spar or elevators were damaged in any way, seems odd that other damage wasn't found or is it just not mentioned.
And what trim setting should have been used if neutral caused higher loads on the right side due to the position of the tab, surely that was the best option.

[Pugilistic Animus]

Djpil, What is "rolling G"?

[Jhieminga]

I've taught that exact same exercise but I would create an out-of-trim force for a low speed situation (trim nose up). That way, I could keep my hand against the yoke to stay level, and guard the yoke against moving back too much by keeping my hand near it. It is much easier to just move your hand back half a centimeter once the student has applied enough pressure, you are then in a good position to reapply force to the yoke if the student releases it inadvertently.

[Fl1ingfrog]

Based wholly on the information provided in the report: this demonstrates both a sloppy and an appalling standard of instructing. For me it is nonsense to excuse what took place by waffling on about whether half of trim travel or three quarters or whatever. Even with the trim fully deflected the instructor should have easily managed the situation in a C152.That was not the problem. The instructor is clearly at fault and hadn't even secured his seat belt correctly. The student obviously had and so he suffered no injury.

This was lesson number 1. The primary effects of controls together with the further effects should take the whole of the lesson and continue until they are fully understood. The effects of controls should be learnt over at least two but better three lessons and the full effect of trim discovered at the end of this period. It is a disaster for the student if these early lesson/s is rushed and skimped. They will be the basis of all subsequent lessons. Given it was lesson 1 how on earth can it be expected that a student will have it in their mind what will happen if they let go of the controls. It must always be possible that a student will let go of the controls unexpectedly. The report describes the instructors hands (and probably his feet) were not in a position to take control but, clearly, nor was his head. How on earth can it take 25 seconds to take control! He was certainly not observing or taking an interest in his student. It must be obvious that his head was somewhere else, he panicked and grabbed at the controls so roughly, even bending the throttle, and warping the tail plane. The aeroplane had clearly been allowed to exceed VNE.

[Waypoint Short]

Djpil, What is "rolling G"?
A rolling G occurs when you maneuver an aircraft in more than one axis at a time, causing the airframe or wing to twist. The rolling G design limit is considered to be 2/3 of the normal G limit, according to FAR 23.

​​​​​From jebriggs blog, I can't post the link sorry.

[WHBM]

I seem to remember this was a known issue on the C152, and special attention to this point in the horizontal stabiliser on aircraft which had been used for training manoeuvres was advised during the walkaround. The C152 Aerobat used a different, more heavyweight tailplane for an aircraft aimed at (limited) aerobatics, and I believe the F152, which was the aircraft assembled by Reims Aviation in France, and common in Europe, used this revised design on all their aircraft. Someone will know a lot more.

[F-16GUY]

Djpil, What is "rolling G"?

PA,

Rolling G occurs when you maneuver an aircraft in more than one axis at a time, causing the airframe or wing to twist. The rolling G design limit is normally considered to be 2/3 of the normal G limit. Normally rolling G will be defined as rolling more then X degrees pr second. For instance, the F-16, rolling G (2/3 of max G) is defined when rolling more then 20 degrees pr second while pulling G's.

[Pugilistic Animus]

Thank you very much F-16Guy.... it's true that you can learn something new everyday

[Big Pistons Forever]

I have seen almost identical damage to a C 152. In that case it was a badly botched spin recovery by an instructor who tried to extend the spin to 3 turns but let up on the elevator so that the aircraft entered a spiral dive. By the time the clueless instructor realized what was happening he was going through redline and then damaged the aircraft with an aggressive pull out.

Personally I am godsmacked that so much damage was done on a simple recovery from a miss trim induced dive. Sadly the "solution" isn't to make sure instructors can actually fly airplanes without breaking them, it is to make more rules at the flight school telling them how to teach students how to trim :ugh:

[LastStandards]

...it is to make more rules at the flight school telling them how to teach students how to trim :ugh:

Indeed. Teaching a student how to Select Hold Trim can be kept pleasantly simple - bearing in mind that it is about attitude flying rather than level/flight path. Displacing a trim control while a student is flying is incredibly poor technique for so many reasons! Far easier and more productive to displace the aircraft into a new attitude, trim, and then give the student control to reselect the original/Datum attitude and note the force required to hold it. Thennnn teaching Coarse -> Fine trim control. I see a significant number of pilots on either training or test flights try to hurry trimming and never actually complete the process, because the finesse was never taught at the initial stages.

[Fl1ingfrog]

Well, that is commonly said; "........bearing in mind that it is about attitude flying" I do not agree. the elevator is used to set the required attitude in pitch. The trim relieves the pilot of the control loads. The trim is not a flight control.

The high load demonstration is important for the student to understand just how overwhelming the trim can be, when mis-set, in some aeroplanes. It should also be a heads up to the importance of the trim pre-flight checks.

[BigEndBob]

Third of all Cessna 152 i have flown have some kind flex in the tailplane. Try moving the tail plane up and down and see if they flex. Some even have the skin crease near what looks like a forward support spar a few inches from the fuselage.

[LastStandards]

Well, that is commonly said; I do not agree. the elevator is used to set the required attitude in pitch. The trim relieves the pilot of the control loads. The trim is not a flight control.

I agree entirely - which is why my full paragraph referred to the process of Select Hold Trim as being about attitude flying.

While it is important for the student to understand the effects of misset trim and the control loads that may be required to hold the desired attitude, it remains poor practice for an instructor to manipulate trim to an unknown position while a student is flying, and indeed goes against the whole concept of a clean transfer of control. By selecting and retrimming a new attitude and then requiring the student to return to a previous attitude and hold the loads will increase relatively slowly, giving the student adequate time and opportunity to quantify the changes - as well as increasing their own confidence in their ability to direct the aircraft using all 3 primary flight controls in their relevant axes. Or so my FI Course students and test candidates have been teaching for a while anyway, without bending aircraft...

[Ascend Charlie]

Dismally inexperienced and unsupervised Grade 3. The Grade 1 who taught this instructor, and the Grade 1 who supervises this instructor, should also be under the microscope.

[Fl1ingfrog]

Dismally inexperienced and unsupervised Grade 3. The Grade 1 who taught this instructor, and the Grade 1 who supervises this instructor, should also be under the microscope.

The grades noted are not what I recognise but are comprehensible. Where the prospective instructor is required to compete a formal course of training it must be unlikely that the FIC instructor would have been tolerant of such sloppiness. This instructor will have been bored and without care allowing his concentration to wander elsewhere. Not even bothering to secure himself and maintain both his feet and his hands at the controls demonstrates his arrogance. The outcome was always foreseeable by any instructor except by a fool.

..... the loads will increase relatively slowly, giving the student adequate time and opportunity to quantify the changes .....

Absolutely, all teaching, to be of any benefit to the student, must first be briefed, even when airborne if that's the way it is, so that the student is always part of it all. There cannot be anything gained by having the student continue flying subject to these loads because that is not the point. Whatever the chosen out of trim experience what is most important are the actions the student learns to take to correct the issue: i.e. maintaining the desired attitude whilst correctly retrimming to balance out the loads. From this exercise the student will have learnt how powerful out of trim loads can be either from a misseting, a jammed trim and the not infrequent runaway of electric trims. How to resolve these last two, being malfunctions, should be dealt with within a separate lesson.