View Full Version : Bank Angle Selector

12th Mar 2004, 17:15
Here nobody cares about selecting low (15°) bank before takeoff or goaround (on the B733/734).

They're apparently too lazy to do that, and/or they thrust too much the performances of the airplane.

If you have an engine failure just after V1, the FD will call for speed V2.

But we know that we can't bank more than 15° until reaching V2+15 at least.

Now, if the departure or the missed approach procedure call for a turn before acceleration altitude, I'm sure everybody will still call "Heading...." or "LNAV", as they usually do.

But that's unsafe, at least in theory. :8 :8

On the 744, for example, with the bank angle in AUTO, you'll get maximum 15° if you loose an engine (out of 4!).

Anybody out there playing routinely with the Bank Angle Selector on the 737 classic?

seat 0A
12th Mar 2004, 18:05
Nope, we leave it at 25 as well.
Nothing to do with laziness, though. It`s just SOP for us. We get taught to ask for "bank limit 15"in case of having to make turns during an engine failure procedure. In 90% of all cases our take off path during an engine failure will be straight ahead until after acceleration. (shouting at ATC where required ;) )

12th Mar 2004, 18:35
In the Avro RJ series aircraft, crews are taught to set the 15 deg bank limit if an emergency turn is part of the departure briefing. This SOP reinforces the awareness of the nonstandard ‘engine failure’ departure and the need to limit the bank at low speed. The initial FD mode is track (TRK). Thus having also set the required emergency turn heading before take off, all the crew has to do is select HDG mode when passing the emergency turn altitude. The pitch mode commands V2, or if higher, the speed at which the engine failure was detected.

A simple, low workload, and safe operation that enhances CRM; - a crew in harmony with the aircraft and the fight guidance system.

seat 0A
12th Mar 2004, 21:05
Sounds good.
Regrettably my company is moving to a "Basic Operating Philosophy"(aka cheaper philosophy), so I don`t think we`ll see any oportunity in the near future for suggestions.
Unless mister Boeing decides to put this in a manual.

14th Mar 2004, 03:44
Hy gents
'Mr boeing' did this:
at take off the 'roll command maintains HDG SEL.Bank angle is limited to 8 degrees untill 400 feet AGL' ( at some a/c this is valid only untill 200'
I suppose that at 400' you'll have at least V2+15,and you'll be able to bank safely at 30 degrees.
Above informations are from OM2,automatic flight /takeoff

14th Mar 2004, 06:07
Another issue about the bank angle selector is when it works. Does it work only in heading select and not in LNAV? Next time you are in a LNAV turn check if you can limit the bank with the bank limit selector….

Dan Winterland
14th Mar 2004, 06:40
On the 744, bank angle selection only works in HDG SEL. I was tought that in the EFATO case, you cancel the SID by going for HDG SEL unless there were overiding terrain considerations. Therefore in most cases, this isn't a problem. In a engine out GA, you will initially be in TOGA mode which holds the runway track or runway heading (depending on PANSOPS or TERPS criteria) until you select HDG SEL or LNAV, so then again applying common sense, there's no problem.

As I understand it, LNAV applies the max angle of bank dependant on your phase of flight. For example, it knows to limit the angle of bank to 15 degrees between flaps one and up until you are VREF+100.

14th Mar 2004, 11:24
Anybody out there playing routinely with the Bank Angle Selector on the 737 classic?

My original question was about the 737, not the 744 (which I cited to make a comparison).

I suppose that at 400' you'll have at least V2+15,and you'll be able to bank safely at 30 degrees.
If you have an engine failure just after V1, the FD will call for speed V2.

Another issue about the bank angle selector is when it works. Does it work only in heading select and not in LNAV?
On the 737 classic, it works only in HDG and VOR.

On less performant airplanes, e.g. ATR 42, people are more sensible to this issue, and it is standard to takeoff with, or to call in a goaround, "HDG, LOW BANK, IAS".

But the principle is the same on a heavily loaded Boeing 737.
So it should be a standard to routinely do the same (takeoff & goaround with bank limited to 15°, until after acceleration).

Annoying in real life, I know, but in a sim ckride a picky controller could easily fail you on that, if a turn is required before acceleration....

Out of topic: congrats to the PPRUNE staff, the new hardware is really amazingly fast!

LEM :ok:

14th Mar 2004, 17:45
The B737 manuals do not give any specific details on what to actually set the bank angle limiter to. It just states “as desired” and assumes that the crew will set it to anticipated bank angles and rates of turn, consistent with the demands of ATC, SIDS etc. during normal operations.

Boeing’s general philosophy is to prepare for normal anticipated operations while taking certain backup steps such as preparing one of the white speed bugs by setting it to aid in limiting bank in case of an unlikely engine failure. Normal departure includes setting the bank angle limiter to more than 15. It is always wise to be prepared for an engine failure but this should not be done at the expense of the most likely events – the normal procedures.

As an example, many city airport SIDS require early turns with a good rate. Airport authorities are constantly sending out letters of warning to operators that have deviated from mandatory early turn tracks. These letters often include compulsory action such as mandatory use of LNAV when available; and to use procedures which will give max rate of turn (e.g. low speed and max bank).

Boeing manuals are written under the assumption that that users are familiar with basic pilot techniques common to aircrafts of this type. One example of this would be not to follow the flight director commands beoynd 15 degrees of bank when below V2+15 on single engine or to change the bank angle limiter for a short period while accelerating to V2+15, another example would be to set bank angle selector to 15 degrees if climbing above optimum altitude while keeping in mind that this will only work in HDG SEL.

22nd Mar 2004, 00:45
On the B-737 why do we use 25 degress of bank angle instead of 30. When engaged in LNAV the airplane will use 30 degress anyways (most of the time, sometimes it will overshoot it a little). I haven´t figured it out yet. Just wanted to catch a ride on LEM´s thread.



22nd Mar 2004, 07:51
Somewhere in the deep, dark brain pit I recall that 25 deg gives Rate 1 at typical speeds?

Dan Winterland
23rd Mar 2004, 18:16
A hold or procedure turn should be flown at rate 1, or 25 degrees AoB max. A rule of thumb is TAS divided by ten plus seven for your AoB for a rate one turn. So an aircraft holding at 230 knots at FL50 will have a TAS of approx 250 knots, divided by ten add seven equals 32 degrees. So 25 is your max in this circumstance.

23rd Mar 2004, 19:06
Gawd bless your brain, DW!:D Got any spare bits?

Right Way Up
23rd Mar 2004, 19:26
The problem I see with presetting the bank angle limit is you are already deciding your failure on takeoff. It is a problem with the majority of sim checking and even departure briefs that we talk about an engine failure at V1. In the sim if you throw an engine failure at a guy at 1000 feet it often completely throws them. Not particularly their fault but just symptomatic of the obsession with V1 cuts. IMHO we should deal with problems as it happens and SOP should direct us to select Bank angle limit of 15 deg when we select the emergency turn heading if required.

Dan Winterland
24th Mar 2004, 09:31
Actually, it's not very big. Just full of junk like the above!

Right Way Up
24th Mar 2004, 18:20
"Junk" - was that in your post or mine??:D

Dan Winterland
24th Mar 2004, 23:12
No, it's definately my brain that's full of junk. Mrs W reckons a lot of my thinking comes from much lower down!

25th Mar 2004, 11:03
Right Way Up, I agree with most of your post, but consider setting the bank angle selector as a precaution rather than ‘deciding your failure’.

The pre-selection of low bank (where warranted) is also a cue to discuss the ‘what if’ aspects of the departure; whereas the use of a SOP after the event is open to error – forgetting, and the stress of the unexpected and often frightening event.

I agree that less focus should be given to V1 cuts; accident statistics show that most pilots can fly the aircraft (exception Turboprop PSM+ICR), it is more often failures in decision and navigation after the initial emergency event that result in increased risk. If an engine fails once airborne then the terrain clearance during a standard departure is a lesser issue, similarly if the failure occurs after the emergency turn point or acceleration altitude then low bank angle may no longer be a requirement.

Thus all aspects of the points above are required to maintain safety; good pre-flight briefing and planning, SOPs, and staying mentally alert to the situation …. all of this with the stress of the failure, loud noises, vibration, loss of secondary services, etc. The simulator is the place for practicing these aspects but so often the machinery and / or the instructor lack that capability … notwithstanding the regulator / inspector’s view which is often clouded by the V1 image as opposed to realism of our industry.

What kills more people in the industry?
1. CFIT (not knowing where you are, - not turning on an emergency turn).
2. Loss of control (not maintaining the correct airspeed / configuration, - not limiting the bank angle at low airspeeds)

There are few new reasons for accidents, only old ones revisited by new pilots.