737 Engine Out Trimming During Turn

[Don Gato]

If -on the 737- one wishes to apply rudder trim IN A TURN (obstacles) after Engine Failure, it does not seem as easy and straightforward to precisely do it and then verify if the aircraft is properly trimmed. We know that in straight flight we should have a levelled control column. However, proper trimming during turns is not as clear (control column position, bank angle, turn rate, etc.). Would like to hear your thoughts with regards to such factors (control column position, turn rate, bank angle, etc.) Thanks!

[parabellum]

Was taught NEVER to trim in a turn, held good for me for nearly forty years. If you get an EFATO and there are obstacles hold the imbalance on the rudder with your own leg power until you are wings level again. (Flew the B737-200 with the -17 engine).

[Don Gato]

Parabellum: Thanks. I agree and do the same, but was wondering if someone has other views. Good to have your experienced advice.

[parabellum]

Don Gato - The other "Never do" in a turn I was taught is extend flaps! :)

[RAT 5]

DG: you are correct; it is very difficult to trim in a turn, and why would you? 180 degrees takes 60-90secs depending on speed. Not too long to hold with your leg. If you feel you have too - there is Never & Should Not & Not Recommended - from the sim exercises I've done for decades the trim settings are noted. If stable on thrust & speed at Up - F15 the zero force trim setting is 4-5 units. If at climb power stable speed it is 9-10.
When trimming, PM can set it for you on command, or you can time it. The trim rate is 1 unit/2secs. So you can set it with eyes still on EFIS and then check it after X secs with a glance.

I endorse the 'should not' in a turn, for trim & flaps.

[Don Gato]

RAT 5: Excellent! Thanks for your reply. I agree on the recommendation of not trimming during turns and also with your trim figures. Would love to hear about your other "Never & Should Not & Not Recommended" statements with regards to the 737. :ok:

[RAT 5]

Be careful what you wish for. I flew with many different outfits who morphed 'not recommended' into an SOP 'not allowed'. The Boeing 'not recommend' was not a 'never', and sometimes was for dubious pedantic reasons. For those who knew what they were doing it was perfectly acceptable, if necessary. Some operators were enlightened & flexible, so it as irritating to be handcuffed by those who dumbed down to the lowest denominator.

[Johnny F@rt Pants]

Would like to hear your thoughts with regards to such factors (control column position, turn rate, bank angle, etc.)

If you are established in a balanced turn your control column should be level, so any displacement away from that requires rudder to prevent skidding or slipping.

With regards to trimming in a turn, the FCTM states words to the effect of that we should fly the aeroplane in trim at all times when workload permits. I would therefore be quite happy for someone to trim the rudder during a turn providing they don't distract themselves from flying accurately. Furthermore, whist it might only take 2 minutes to complete a full 180º turn at 15º AOB, should the PF become incapacitated during that early engine failure turn due to the stress, and say have a heart attack, the PM will have virtually no chance of recovering the situation, however if even some trim has been applied, then their chances have improved dramatically.

As an instructor on the B737, I teach to trim when you have the opportunity, if your capacity is reduced whilst maintaining V2 round an awkward EFP then don't compromise flying the aircraft to do it, but do it sooner rather than later.

[RAT 5]

On NG there is always the slip indicator. During SE ops, it is not the primary source for rudder trimming, and with a level control column it can be a sniff out of centre. If you absolutely had to trim in a turn I'd be aware of what this indicated for some help.
There is a huge difference in not 'red marking' some one for trimming in a turn if they understand what they are doing, can achieve it successfully without compromising a/c control, and they are aware of the consequences, and actively teaching it. In 'teaching it' that could be to first time jet pilots who might not qualify in all points of my previous comment. Dangerous to take one small snippet of FCTM to over-ride another.
If a pilot can not sustain rudder control for a complete turn I'd rather advocate some gym time than trim time.

should the PF become incapacitated during that early engine failure turn due to the stress, and say have a heart attack, the PM will have virtually no chance of recovering the situation, however if even some trim has been applied, then their chances have improved dramatically.

If that is the best reason to teach a debatable technique........well.....?

[Chesty Morgan]

What is the big deal about selecting flaps in a turn?! Happens hundreds of times a day!

[+TSRA]

Quite right, but selecting the flaps during a turn where one engine inoperative does not. The EOP might specify a turn is to be completed at V2, in which case you cannot raise the flaps as V2 will be below the flap retraction initiation speed.

[RAT 5]

This discussion is about operations on 1 engine. Flap selection during a turn is a possibility on arrival. You have the a/c rudder trimmed out/in balance nicely with a stable thrust & speed. Boeing's advisory for correct rudder is level aileron control. You are now in base turn, start to extend flaps and by consequence need to slow done and thus reduce thrust. The trim/balance you had is now not correct. You are in a turn and the aileron control is now not so easy to assess. hence the difficulty to achieve perfect balance and hence the 'not recommended' comment.
I used to emphasise that, using KISS principle, it was easier to have F5 and stable speed before the base turn and thus there was no configuration change needed during that turn. If you do that on 2 engines why make it more difficult during an NNC on 1 engine?
To demonstrate this to students, who wanted to do it differently and delay everything, including being level flight, I would give an ATC descent & a speed reduction instruction; just after they started to execute these I'd give a base turn HDG. Not a shortened finals; distance was fine. With A/P in CMD they ended up in a right turn with the ailerons turning left and didn't seem to think there was anything wrong. I'd then point this out and the slip indicator and ask why they thought this 'unusual' behaviour was happening? The eyes opened somewhat. We'd then reposition to platform altitude, F5 and stable, and fly the base turn manually in level flight and constant speed. In fact it needs a 2-3% increase in N1% that should be applied before the turn and a squeeze of foot to compensate, then turn. As you roll out they are removed. KISS. Which did you find easier? there was a sizeable majority in favour of.

[parabellum]

What is the big deal about selecting flaps in a turn?! Happens hundreds of times a day!


No idea what is taught today but the main reason for not selecting flaps in a turn is to avoid the possibility of having to deal with an asymmetric flap condition, should it occur. If it does occur then it is, I assure you, quite a big deal!

[RAT 5]

Let's not cloud the issue. We're discussing configuration changes on B737 engine out NNC, not 2 engines normal ops.

[172_driver]

Hopefully the seat of the pants flying will tell you’re pressing the rudder about right, in a turn as well straight and level. In the sim there is no seat of the pants flying. I have yet to see anyone complete a sim session without flying out of trim, to a varying degree, for a good portion of it. ;)

[RAT 5]

May be; but why would an average pilot choose a more difficult option when there is a more easy one? Just because the aces can do it why not teach & recommend the easy way to all and sundry and then the aces can choose to play from the rough instead of the fairway if they want. Extending flaps in the turn, SE, is likely to apply only to the base turn, or perhaps to finals if a long way out. It will be a choice to delay configuring. It will also be a choice to configure early on that once in lifetime scenario so you can be relaxed and stress free about it; and your mate. Delaying and risk being rushed, and possibly increasing the workload for both of you, unnecessarily, just doesn't seem the best move. Why would you. KISS seems appropriate.
We are not discussing if you can or can't, it's more of is it the best decision when 'called upon to perform' in that single moment in your career.

[172_driver]

My thought was to put my penny worth in to the original poster about trimming in a turn.
I don’t think there is any way to judge proper trim needed by looking at the control wheel. Level control wheel does not go hand in hand with what you learn on your second or third flight in basic training; Look out, apply aileron, rudder, slight back pressure, opposite aileron and release some rudder.. The amount likely varies with airspeed, bank angle, airframe. The only thing that tells you if you’re skidding/slipping is the turn coordinater and seat of the pants. It was easy to tell in a twin prop when your student did it right and when they were struggling with coordination.

About the flaps in turn, I think everyone will judge there and then if they feel they’re on top of it and ready to extend flaps. Turning or not. I guess it doesn’t happen too frequently these days someone is flying a single engine ILS in real life.

[RAT 5]

I guess it doesn’t happen too frequently these days someone is flying a single engine ILS in real life.

Precisely.

On B737 finals is flown F15. I start with this premise. On a normal circuit, descending or level, it is common to be F5 at least abeam the threshold. Get it under control. Thus on SE the only further flap selection is to landing flap 15 with gear down. It is not recommended = lots of thrust, to fly level in that configuration. Thus it is highly unlikely anyone would be configuring from F5 - F15 in a base turn. All approaches should have a basic plan in mind before commencing them, not just a wing & a prayer, suck it and see while it rolls along. One item in the plan is where I'd like to be F5. It is premeditated. It can be changed to suit unforeseen circumstances, but hey, that's life. That change is likely to be an extended circuit, not a shortened one; i.e. no rush. You might even stay clean until on a longer finals = no turning.
So the question is; if you believe that it is more difficult to extend flaps, slow down and keep the balance while in a turn than in straight flight, why would you predetermine to do so? If it is a normal sized circuit, and you are configuring from Up - F5 in base turn, it would suggest you have deliberately delayed the initial configuration to flap settings less than that for landing. Why would you when it is an infrequent NNC manoeuvre and one you would not do under normal circumstances?
If you don't believe this is more difficult an approach technique SE, then we shall agree to disagree. (I didn't say must not, or can not, or too difficult.) No bother. I know how I will (would have) done it on the day; but to teach that it is perfectly OK and not advise the alternative is................There are many low experienced guys out there whose handing skills are not as sharp as yours and need guidance about the KISS principles.

[172_driver]

Absolutely, in the beginning it was most helpful with some canned numbers and techniques to fall back on. I don’t disagree.

[RAT 5]

Let's hope you don't ever need to test it.

[Don Gato]

FCTM on SE flight technique: "Make turns at a constant airspeed and hold the rudder displacement constant. Do not attempt to coordinate rudder and lateral control in turns" (7.3).

It supports RAT 5's argument and also suggests the difficulties of unbalancing forces while turning, unless necessary.

[Chesty Morgan]

This discussion is about operations on 1 engine. Flap selection during a turn is a possibility on arrival. You have the a/c rudder trimmed out/in balance nicely with a stable thrust & speed. Boeing's advisory for correct rudder is level aileron control. You are now in base turn, start to extend flaps and by consequence need to slow done and thus reduce thrust. The trim/balance you had is now not correct.

Well, ok. But why reduce thrust?! You've just increased drag so you will slow down anyway. There's no rush to get to your newly desired speed.

[RAT 5]

I question that selecting F1 or F5 is significantly increasing drag and will slow you down at the required rate. It takes 3-4nm to make a 180 turn from downwind onto finals. From UP -F5 is 40kts. I hazard a guess that you will not achieve that at the thrust setting you had for UP speed.
No rush: indeed there should not be, and there will not be if it's all under control. To allow your technique to be used, and speed to bleed so slowly, you would need to extend downwind to a longer than normal final. Quite unnecessary. If the a/c is in balance and on speed it will fly and be as manoeuvrable as normal. Single engine just means less thrust to accelerate, accurate management of energy and accurate coordination of all flight controls. (Normally the rudder looks after itself on all engines.)
I hark back to my question: there is an easy method and there is a less easy method. Why choose the latter? You might/should be able to handle it if it is thrown at you, but why choose to have to do so?
The definition of a skilful pilot is.................................IMHO and has been quoted on here many times by those better than I.

FCTM on SE flight technique: "Make turns at a constant airspeed and hold the rudder displacement constant. Do not attempt to coordinate rudder and lateral control in turns" (7.3).

There is a thread under discussion on another forum. The pilot asks for help on the use of flaps for take off in an SEP and rotation techniques under differing conditions. A very common answer from those of experience has been RTFCTM, or Pilot notes in that case.

[Chesty Morgan]

Well no, extending downwind required isn't required if you start configuring in a timely fashion. There is no required rate of deceleration, that's an ATC nicety and when I'm on a mayday they can sling it.

You talk about keeping it easy and the easiest way is to minimise thrust changes. In fact if you get it right the only thrust change required is a reduction when you've captured the glide.