Jet Engine Out Bank Angle

[megan]

Elsewhere on the forum there is a post implying (perhaps to this reader) that an engine out on a 737, 777 etc is flown with the ball centered. Fact, or do you still bank (how many degrees?) towards the live? Reading the drills on the net it talks of pitch angle, among all the rest, but no mention of bank.

Many thanks.

[john_tullamarine]

Several considerations -

(a) at much lower than normal speeds (at/near Vmc) one needs to crank in some bank (certification limit is 5 degrees) towards the operating engine(s) to achieve expected handling characteristics. Achieved Vmc is very bank angle dependent. Climb performance is not the name of the game at this sort of speed .. staying right way up is. Indeed, there may well be no climb in this speed region .. the aircraft often will be in a descent.

(b) once the OEI situation is sorted out and the speed is up at/near the optimum climb speed, best climb performance is achieved with 2-3 degrees for most aircraft. This is a fairly demanding flying exercise for other than a short period. Hence one normally trims out the control loads to suit.

(c) some attitude systems don't like small bank angles so the technique is to fly wings level and accept a small loss in climb performance. Alternatively, if terrain clearance is not super critical on the day, the pilot probably will prefer to fly wings level due to the reduced workload. Some aircraft will have spoiler deployment with other than a "level" control column so that is a driving concern, for such Types, towards flying wings level.

(d) at higher speeds, the need for bank is minimal and one normally chooses to fly wings level.

(e) flying straight with any bank angle, you won't have a centred ball .. it will be displaced somewhat towards the low side. Conversely, wings level, the ball should be centred as there will be no force to displace the ball from centre.

Piston, jet, glider, rubber band powered model aircraft ... makes no difference to the ball situation.

Pitch angle will be appropriate to speed, thrust and Type.

[wiggy]

Megan


Elsewhere on the forum there is a post implying (perhaps to this reader) that an engine out on a 737, 777 etc is flown with the ball centered. Fact, or do you still bank (how many degrees?) towards the live?

This may well be type specific, etc...I can't speak for the 737 but as far as the 777 goes the general principle is to ensure the aircraft is trimmed/flown in such a way as to keep the control wheel centred in straight flight.That's actually the general trimming technique for the aircraft, regardless of engine out or not, and there's a scale on the top of the control wheel hub to help do this. TBH the slip/skid indicator on the PFD (there's no old fashioned ball as in a turn and slip) is not much used. So in short, no you wouldn't be looking to fly with the ball centred and you wouldn't be looking to deliberately fly one wing down on a 777.

[aterpster]

Wiggy:

During my early years on the 727 we had a real turn and bank indicator. That big ball was great for OEI. Then, the FAA deleted the requirement to have that real T&B, so the company removed them. The little ball below the FD-108 attitude indicator was useless, so we had to get used to using the control will to achieve the proper rudder input. That took a bit of getting used to.

[aterpster]

j.t.:

(a) at much lower than normal speeds (at/near Vmc) one needs to crank in some bank (certification limit is 5 degrees) towards the operating engine(s) to achieve expected handling characteristics. Achieved Vmc is very bank angle dependent. Climb performance is not the name of the game at this sort of speed .. staying right way up is. Indeed, there may well be no climb in this speed region .. the aircraft often will be in a descent.

What about in a Part 25 transport jet OEI where V2 is achieved during rotation and lift-off? We were taught to keep the wings level unless we ran out of rudder. I believe that happened only on our old fleet of Convair 880s.

[galaxy flyer]

The best thing since sliced bread was the big ball that popped up in the HUD upon detection if engine loss. Dead cinch to see and relate to flight path and bank angle.

[john_tullamarine]

What about in a Part 25 transport jet OEI where V2 is achieved during rotation and lift-off?

Will depend on the Type, weight and the speed schedules. If you are well above Vmc (as indicated by V1's increasing with weight) it is all pretty straightforward.

For instance, the older 737 classics, at minimum weight, end up Vmc-limited and the V1 failure OEI gyrations in the sim (until the folk up front get on top of things) are a sight to behold.

Like anything, train to meet the need .. for initial commands and intake F/Os, I used to find time to work the folk up to a min V1, max aft CG failure (using the worst engine damage model on the sim), with a min vis situation and a requirement to fly the opposite localiser. Took a few workup runs, naturally, but most were able to end up flying it like it was rails. Thereafter, of course, routine failures were a bit of a yawn for them.

Problem, as I recall (long time since my 727 days) with the FD108 was the small bank angle's driving an ADI response which just confused the issue.

So far as the OP is concerned, though, wings level gives centred ball, a bit of bank angle shifts the ball out to the low side a tad.

The best thing since sliced bread

I'm just jealous that I have never had the opportunity to fly a HUD-equipped machine ... are you out to Avalon next week ?

[Cough]

787 flies slightly wing down when climbing out single engine close to V2...

[aterpster]

Cough:

I suppose that is all done precisely by the auto-flight system.

[galaxy flyer]

No, I'm retired! Actually, being retired means I could go, no boss to interfere. Just last month, but the HUD made it easy.

[megan]

I asked the question after reading an accident report involving a Super King Air 200 where trials were done and produced a ROC of 302 ft/min with 5° of bank into the live engine and 287 ft/min wings level. Does this mean that banking is only important to optimising ROC on FAR 23 types?

[john_tullamarine]

Oh dear ... can you cite the report, please ? It probably warrants a looksee and comment to answer your question in more detail.

produced a ROC of 302 ft/min with 5° of bank into the live engine and 287 ft/min wings level

First up, 5 degrees relates to Vmc i.e., handling rather than performance.

At or around the optimum climb speed, a bank angle of 2-3 degrees (as a general rule) will produce the best result .. I don't know explicitly what the situation is for the KingAir but it will probably be much the same.

Climb performance measured against speed will look a bit like an upturned cup graph. Hence the importance of getting to and maintaining blue line.

Against bank, the graph is a bit more complicated as the direction of bank has a significant effect on slip. However, typically, for the 2-3 degree optimum situation, climb wings level and at 5 degrees should be somewhat similar and slightly less than optimum.

For the figures quoted, they are meaningless unless we know the rest of the test card point story .. speed, technique, etc. At this stage, all they suggest is the truism that climb performance varies with bank angle.

Does this mean that banking is only important to optimising ROC on FAR 23 types?

FAR 23/25, model aircraft, whatever .. all same same. Back in the lower speed end of the envelope, bank critically affects OEI climb performance. Ergo, you can find a bank angle to optimise climb. At higher speeds, the effects are much smaller and, in general, can be ignored. All to do with sideslip angles, both for the Vmc and climb performance case.

[megan]

Was the VH-AAV accident John. Page 19.

https://www.atsb.gov.au/media/4016822/802-1017.pdf

[john_tullamarine]

The data tabulated p19 doesn't have enough explanatory data to draw much in the way of discrete conclusions. However, the numbers trend in a manner one might expect to see.

Certainly, there is not enough data to draw any conclusions regarding specific performance as a function of bank angle

There is no explanation why there is an apparent preoccupation with 5 degrees bank at the climb speed. I'll see if I can find any OEM guidance on the subject. Certainly, I would have expected that the climb target would have required somewhat lesser bank.

What the data do suggest, however, is the folly of homegrown reduced thrust takeoffs (presumably) driven by engine cost considerations but without any thought to weight reductions appropriate to maintaining OEI performance margins.

[megan]

The single engine climb charts make no mention of bank, the associated conditions are listed as, max continuous power, flaps up, gear up, prop feathered, with adjustment if ice vanes are extended. Don't have the King Air emergency pages though to see what they say there.

Was just intrigued John as the FAR 23 manuals I've seen make a point about bank in the event of a failure, and they use the 5° figure. Their performance charts even include the 5° bank as one of the associated conditions, unlike the King Air chart. Whether you actually get to climb though is another matter.

[john_tullamarine]

Looking at my file POH (which covers AAV, although at a later amendment status than the mishap) bank guidance is somewhat delightfully vague.

You need to refer to the Safety Information Section for anything of use.

Vmc references are pretty standard ("not more than 5 degrees of bank"). However, for performance climb it gets a tad rubbery. There are references to "aircraft flown at recommended bank angle" under the section on Vyse (but without defining what might be recommended), and "the airplane must be banked about 5 degrees into the live engine" under the section on basic single engine procedures. I guess the poor old pilot needs to be a bit of a mind reader (or do a lot of general research reading).

I would revert to my previous thoughts. Near Vmc target 5 degrees bank into the operating engine while, for Vyse, perhaps 2-3 degrees (if performance is super critical on the day - otherwise wings level) and, for higher speeds, wings level.

Nothing that I can find in the emergency section (Section III).

So far as the run of the mill manuals, one needs to keep in mind the litigious nature of the US environment and a reluctance to provide guidance other than to the extent required by regulation. 5 degrees, at least, is referred to in the Regs.

[megan]

Thanks muchly John, I think that wraps it up. Of the two FAR 23 manuals I have one is of 1979 vintage and the other 1981, a little prior to the sharks getting their teeth into GA in a determined fashion and decimating same, though they've always been there circling.

[zzuf]

JT
Typically during certification 5 degrees of bank will be used for Vmc determination to achieve Vmc min. More bank (not permitted) will give an even lower Vmc.
Climb performance speed speed is established by sawtooth climbs bracketing a speed range, then performance is measured at that speed. Invariably this is at 0 degrees sideslip, at the bank angle required for zero sideslip. The bank angles you suggest fit with my experience.
The flight test aircraft will have an alpha/beta probe (angle of incidence/sideslip).
In the real world, in some aircraft zero sideslip is pretty easy to pick, in others very difficult without dedicated instrumentation. Pretty well all conventional jets will have zero aileron hand wheel angle at zero sideslip due to normally strong rolling moment due to sideslip. All bets off for FBW, but one could select the flight control page and adjust rudder until zero aileron angle at zero roll rate is achieved, not that this would be in any way practical. Propellors complicate things by prop wash induced rolling moment.
There may be operational reasons for climbing at other than zero sideslip.
Not meant as an egg sucking lesson but to add to the general conversation.
Have fun at AV.

[john_tullamarine]

Good sir, we'll have one (or three) for you at the symposium ..

in others very difficult without dedicated instrumentation

Bellerophon posted a pic of the Concorde gauge (http://www.pprune.org/1085835-post18.html) .. talk about snazzy.

There may be operational reasons for climbing at other than zero sideslip.

Apart from workload and things like the FD108 limitations mentioned earlier ... and only showing my ignorance here .. can you elaborate ?

[zzuf]

I was thinking of those cases where the trainers have decided wings level or skid ball central is an easier option than trying to determine the required bank angle and those steam driven attitude indicators which try to erect to a "false" vertical at small bank angles (as you mentioned).
When manoeuvres are required it is very difficult to maintain zero sideslip even with beta indicator - constant rudder force seems ok (at constant CAS). I know this wasn't part of the original thread subject but may be part of an escape flight path.
When I did my Canberra training (nearly 50 years ago) the RAAF was firmly skid ball central at all times. I clearly recall turning base, asymmetric, with almost full left rudder and the aileron hand wheel bumping the right stop in turbulence! I suspect this technique may have contributed to at least one loss of control incident. The fix was back off half the rudder deflection, and the ailerons returned to about neutral - who cares where the skid ball was!
Later at ETPS an instrumented Canberra was available to clearly demonstrate the folly of the RAAF technique.
I believe the RAF lost a Hunter which had an asymmetric external fuel tank jettison, the pilot was told "simple, just keep the ball centered", I think it was in manual reversion with limited aileron authority. Anyway it departed rolling rapidly in the direction of the applied rudder.

[john_tullamarine]

Thanks for the clarification.

While not having had the military pilot exposure personally, other military involvements from time to time certainly have indicated some strange ideas in the QFI fraternity.

[Cough]

Cough:

I suppose that is all done precisely by the auto-flight system.
Flight control system provides correct application of rudder. Pilot follows guidance cue in HUD. Net result - Wing down (slightly)!

[twochai]

FAR 23/25, model aircraft, whatever .. all same same

Not always true!

The flight test guide does permit up to 5 degrees bank angle for use during performance testing, which reduces the rudder angle required to keep the aircraft straight, thereby reducing drag in the OEI situation, generally speaking.

However, the performance benefit is certainly variable according to the aircraft's aerodynamic configuration, i.e. if the aircraft is equipped with spoilers for lateral control, some aircraft may, or may not gain a performance advantage with 5 degrees of bank, depending on control wheel deadband angle characteristics when out of center.

The aero guys will fine tune control wheel deadband during flight test according to the actual characteristics desired, before freezing the production configuration. Pilot Induced Oscillation (PIO) sometimes becomes an issue here.

This may explain why the 777 calls for zero bank on climb out with OEI (doubtless helped by the aircraft's relatively high power to weight ratio compared with older designs).

[john_tullamarine]

The flight test guide does permit up to 5 degrees bank angle for use during performance testing

I think we need to isolate the Vmc handling and optimum climb situations for the benefit of those coming up the training pipeline. There is a great deal of misinformation and ignorance in the GA fraternity, especially.

if the aircraft is equipped with spoilers

Of course OEM AFM guidance is observed. However, unless spoiler operation commences with a very small wheel deflection, this won't necessarily be a problem. In any case, as zzuf observes, swept wing often favours something in the region of wheel level. If I recall from my Boeing days, spoilers came in at around 10 degrees wheel deflection ?

I'll leave the finer detail explanations to the certification TPs on the site, such as zzuf. (I am presuming you have a TP background but your profile provides no guidance as to what your specific background might be ? If my guess be correct, you may well know zzuf).

[underfire]

when designing EO RNP procedures, turns are limited to 5° bank angle.

[john_tullamarine]

when designing EO RNP procedures, turns are limited to 5° bank angle.

Can you cite a relevant document/Standard for perusal, please ? 5 degree bank would be very difficult to sign off on due to

(a) piloting difficulty unless it be autoflight

(b) the huge turn radius and flight path wind sensitivity for skirting nasty obstacles ...

15 degree turns are the norm for EO escape path planning. Generally one would only call up lesser bank in the case of an awkward obstacle on the inside of the turn .. and then only with a positive fix co-ordinate to commence the turn.

All these matters can be addressed with modern nav system capability .. but that infers considerable planning behind the procedure.

[Goldenrivett]

john_tullamarine #2. Achieved Vmc is very bank angle dependent.

Please see appendix 5 of G-APFK_Append.pdf (https://assets.publishing.service.gov.uk/media/5422f2fde5274a1317000455/6-1978_G-APFK_Append.pdf).

Full report: 1978_G-APFK.pdf (https://assets.publishing.service.gov.uk/media/5422f2fced915d1371000437/6-1978_G-APFK.pdf)

[john_tullamarine]

Full report

This report is cited from time to time in PPRuNe discussions on this sort of subject .. indeed, I used its content in briefing sessions in a past life.

Recommended reading for all young would-be heavy aircraft pilot folks ...

[oggers]

undefire

when designing EO RNP procedures, turns are limited to 5° bank angle.

Really?

TERPS: These criteria are predicated on normal aircraft operations for considering obstacle clearance requirements. Normal aircraft operation means all aircraft systems are functioning normally


PANSOPS: 1.1.2 Procedures contained in PANS-OPS assume that all engines are operating. Note.— Development of contingency procedures is the responsibility of the operator.

What is your reference for designing EO RNP procedures?

[zzuf]

Vmc is not really bank angle dependent.
Any manufacturer which chooses to use less than 5 degrees of bank, and any certification authority which will not accept 5 degrees of bank at Vmc are not using the certification standards as envisaged by the authors.
Vmc is simply a well defined certification speed.
Nobody has mentioned if the AFM Vmc has been determined as a static Vmc or dynamic Vmc. How would you know?

Some posters here probably would be astounded at the minimum speed which can be safely reached using no rudder and only bank to control yaw in an engine inoperative situation - assuming stalling is not a problem.
It can be safe to fly many aircraft around, one engine inoperative, take-off power on the other, at speeds well below Vmc. The speed reached in these circumstances is not Vmc - that speed has already been defined during certification.
It is simply a defined certification speed, for the reason of hanging oeio performance standards together.
It has nothing to do with the "loss of control speed".
If you are flying at around Vmc and are thinking you may lose control, not about to stall, roll on more bank, could be better than the alternative!

[Derfred]

I'm no knowledge expert but if my memory serves the RNP procedures are designed with up to 50kt adverse wind. Certainly the approaches are, not sure about the departures. That could explain the 5 degree bank restriction. In maximum adverse wind, in reality, that bank will increase, obviously.

[john_tullamarine]

Vmc is not really bank angle dependent.

Indeed. However, this relates to the certification book Vmc speed.

Operational discussions out in the marketplace on bank and low speed directional control problems need to distinguish between the

(a) AFM Vmc book value (ie the certification animal which is well defined but of little precise value to the GA pilot in the street) and

(b) the rubbery low speed OEI directional control problems in the real world on the day which are sensitive to whatever bank is applied ... we use the term "Vmc" rather loosely and imprecisely in this latter case.

His comment regarding using a tad more bank is a key to delaying a departure early in the low speed OEI recovery.

[zzuf]

Re-reading my previous post, it could give the impression of a cavalier attitude to Vmc.
Vmc determination can be one of the most hazardous certification test procedures, with a high risk of departure at low altitude.
Work up should be done in, preferably, the engineering simulator. Plenty of departure recovery training, with PNF or flight test engineer responsible for rapidly closing the throttle of the operating engine as necessary.
In-flight work-up at a safe altitude. Don't do the low altitude tests until the test team are totally confident that a departure won't occur.
During these work-up test you will surely see speeds below what ends up being Vmc.
If the certification authority will accept some analysis in lieu of the really hazardous low altitude tests, grab the opportunity.

[LH777]

In the B737NG and B777 sim centering the control column when OEI will give you a few degrees of bank towards the live engine.
Documented in the FCTMs I think.