Bank Angle maximum 15° till 1500 AGL

[B737NG_Pilot]

Bank Angle maximum 15° till 1500 AGL - Why? This is mostly seen in E/O Departures.

[tmpffisch]

Increasing bank angle increases load factor, reducing the margin to stall. A larger bank angle would require a faster speed to be flown, reducing E/O climb performance.

[Tinstaafl]

I can think of 3 reasons:

1. Regulation: The amount of manouvering during the initial stages of a SID is limited by procedure design recommendations to reduce workload & errors during that critical transition phase.

2. Performance based obstacle clearance: If you are already at a maximum performance airspeed, climb rate (and therefore gradient) reduces as bank angle increases.

3. Navigation based obstacle clearance: Turn radius (and therefore ground path radius) reduces as angle of bank increases.

[A37575]

Certainly not a recommended procedure by the manufacturer.

[john_tullamarine]

Bank angle equals load factor increase which is essentially similar to increased weight for performance .. not a really good idea OEI.

Presumably you are aware that the AFM specifies a gradient reduction for climb calculations for turns ?

15 degrees is more than enough to create difficulties with terrain critical departures OEI.

I notice that you have a similar thread in another forum. Against site rules, I'm afraid. I'll leave this one run as it is appropriate to Tech Log. However, please don't run multiple threads as that is a good way to end up in the sin bin.

[vapilot2004]

I have always thought the limitation was there to control track deviations at low altitude. Also a wing down on a transport size aircraft will reduce your obstacle clearance by 20-30 feet, depending on span and bank angle.

[john_tullamarine]

I have always thought the limitation was there to control track deviations at low altitude.

Not to my knowledge. It is presumed that the pilot can manipulate with a reasonable modicum of skill so track locus is reasonably well controlled. The track splay is intended to take care of minor tracking errors.

Also a wing down on a transport size aircraft will reduce your obstacle clearance by 20-30 feet, depending on span and bank angle.

If you scale, say, B707/DC8 at 15 degrees, you will find that the loss is around 15 ft .. hence the 35/50 delta for straight/turning departures.

[TheChitterneFlyer]

It much depends upon performance legislation, i.e. the State in which the aircraft is registered and compliance with the local authority. For example, the UK TriStar (RIP), had flight manoeuvre limits of 15 degrees of bank, whereas in the USA (for an FAA registered aeroplane) the limit was 30 degrees of bank. Min Manoeuvre speeds for retracting the flap are predicated upon the bank angle, hence, should there be an engine failure after take-off you're within the speed bracket; erring upon the safe side.

[Mach E Avelli]

V2 min is only 1.15 or 1.2 Vs (depending on aircraft certification). Coupled with the other problems brought on by unexpected engine failure, this is not much of a margin above stall, so is probably the main reason for the 15 degree bank angle limit.
If a V2 overspeed is permitted ('improved climb'), although the close proximity to stall is then not such an issue, the takeoff analysis should still assume any turn below 1500 feet will be at 15 degrees bank angle and take into account the greater turn radius.
Some SIDs which require a low level turn after take off may state minimum bank angle greater than 15 degrees. V2 should be increased in the analysis to cover this.

[BOAC]

Bank Angle maximum 15° till 1500 AGL - Why? This is mostly seen in E/O Departures. - Please state your reference for this and cut and paste the words here so we can make head or taii of this. What is your standard company acceleration height?

[HazelNuts39]

Bank angle maximum 15 degrees is not an operating limitation. It is a limitation for the regulatory demonstration of E/O obstacle clearance. For that demonstration it must be assumed that the bank angle does not exceed 15 degrees. It applies until clear of obstacles, which may be higher than 1500 AGL.

[RAT 5]

Ref B737 family. 15 Bank Angle is likely only required if flying < V2 +15. This a manoeuvre margin certification issue reflective to Vs. It applies to any time time you are below this speed for the flap configuration. This will apply with an engine failure on takeoff and when an 'emergency turn' is required. It should be required until the first turn is completed and above MFRA. The 1500' consideration could come from obstacle clearance only being considered up to 1500' above the airfield. It is true that less bank angle = better climb performance, but that comes into the obstacle clearance calculation and any emergency turn routing and MFRA requirement.

[TheChitterneFlyer]

It matters not whether it's the B737 family or any other family. It's a regulatory requirement which, as previously stated, is governed by each country's aviation authority. A UKCAA or a USA FAA regulated (identical) aeroplane will each have a different bank angle limit; 15 or 30 respectively.

[vapilot2004]

Not to my knowledge. It is presumed that the pilot can manipulate with a reasonable modicum of skill so track locus is reasonably well controlled. The track splay is intended to take care of minor tracking errors.


Considering different classes of aircraft will require varying degrees of bank angle to alter their track a similar amount, this makes sense. Thank you Sir John. Also understand and agree how the maths clearly illustrate the vertical clearance reduction by having a wing down on a large aircraft - we know this is the key factor driving AFM bank angle limitations under 50 feet AGL.

Perhaps in designing the SID procedures, bank angle limitations are a regulatory accommodation that allows for different aircraft performance characteristics. Stay within the guidelines, and all aircraft will be able to safely navigate the prescribed course, including aircraft with an engine out.

[underfire]

Bank angle maximum 15 degrees is not an operating limitation. It is a limitation for the regulatory demonstration of E/O obstacle clearance.

There are no public criteria obstacle surfaces, nor public criteria, which takes into account engine out.

If you are following an EO SID procedure, you would need to verify that your aircraft can follow the procedure min climb gradient, and with enough speed so as to not exceed the bank limit.

If you cannot, you cannot use the procedure.

If I remember correctly, there are many aircraft which are bank limited even further than this below certain altitudes. (arent 747/777 limited to 8 degrees below 1000 ft?)



Also, per the FAA procedure design guidelines: 8260.58 (this should really clear it all up!)

Basic information.

Except as limited by the rules below, the standard design bank angle is assumed
to be 18 degrees (14 degrees for CAT A-only procedures).

The maximum bank angle is:

Fly-by turn rule: One-half the magnitude of track change for turns less than 50 degrees; 25 degrees for turns equal to or greater than 50 degrees (20 for RNP/ATT less than 1.0). Maximum bank angle below 500 ft above airport is 3 degrees.

Fly-over turn rule: Determine the OEA outer boundary radius based on standard bank angle. For segment length calculation, maximum bank angle is 25 degrees.
Maximum bank angle below 500 ft above airport is 3 degrees.

RF turn rule: Calculated RF bank angle based on the design radius is not to exceed 25* degrees (20* for RNP/ATT values less than 1.0). Maximum bank angle below 500 ft above airport is 3 degrees.
*15 degrees for CAT A and B-only procedures

[elcol]

A good reference is Getting to Grips with Aircraft Performance.
Available here:Getting to Grips With Aircraft Performance (http://www.smartcockpit.com/aircraft-ressources/Getting_to_Grips_With_Aircraft_Performance.html)


Read pages 62-74 and note the difference between the regulatory requirements of FAR and EU-OPS

[A37575]

Reading the OP. Is he saying the FD bank angle selector is required by his company SOP to be set at 15 degrees on all take off's (in case an engine failure occurs in the climb to 1500 ft) and not changed until above 1500 ft? The 737 has a bank angle selector for the flight director. Most operators I know of have it set at 25-30 degrees for normal flight. If the departure requires a curve after engine failure at V1 then it is a simple movement to switch the angle of bank limitation on the FD selector to 15 degrees. As the gradient of climb varies only a slight amount between V2 and V2 +20, then even if an engine failure occurs seconds after lifting off, the aircraft will have already accelerated during the rotation sequence to V2 + 15-25 and a 30 degree angle of bank is quite legal and safe.

It is unnecessary and proves nothing, to limit the angle of bank to 15 degrees on all engines until reaching 1500 feet - just in case an engine should fail before 1500 ft.
However I may have misunderstood the full meaning of the original post

[aterpster]

underfire:

Also, per the FAA procedure design guidelines: 8260.58 (this should really clear it all up!)

Basic information.

Except as limited by the rules below, the standard design bank angle is assumed
to be 18 degrees (14 degrees for CAT A-only procedures).

The maximum bank angle is:

Fly-by turn rule: One-half the magnitude of track change for turns less than 50 degrees; 25 degrees for turns equal to or greater than 50 degrees (20 for RNP/ATT less than 1.0). Maximum bank angle below 500 ft above airport is 3 degrees.

Fly-over turn rule: Determine the OEA outer boundary radius based on standard bank angle. For segment length calculation, maximum bank angle is 25 degrees.
Maximum bank angle below 500 ft above airport is 3 degrees.

RF turn rule: Calculated RF bank angle based on the design radius is not to exceed 25* degrees (20* for RNP/ATT values less than 1.0). Maximum bank angle below 500 ft above airport is 3 degrees.
*15 degrees for CAT A and B-only procedures

Those are design criteria for RNAV instrument approach procedures. They have nothing to do with departures, much less OEI departures.

[underfire]

This is used for RNAV DEP and RNP 1 DEP. I would suspect that SID DEP would be similar.

Yes, there is nothing in any criteria for EO anything.

[john_tullamarine]

there is nothing in any criteria for EO anything

Generally an operator/commander consideration in the application.

The basic certification/AFM data is used to match RTOW against runway distances and departure terrain clearances to cover the takeoff failure case.

Indeed, the AFM consideration is driven by the OEI case.

Considering that EVERY heavy takeoff considers and calculates OEI requirements ... to suggest that there is no EO criteria is somewhat fatuous, I suggest ...

[vapilot2004]

Is our thread starter asking about AFM/Company Limits or regulatory limitations. I have seen both at work in the area of bank angle and OEI recommendations, but am not sure which we are all talking about here.

Aterpster: You are our plate/procedure/NAV publication Guru, or so I thought. What are your thoughts on the original question?

[john_tullamarine]

Leave the plate work to aterpster .. he knows all about that heavy stuff.

However, AFM/regulatory OEI limit generally is 15 degrees due to climb degradation. Company procedures may reduce this for specific escapes generally to constrain turn radius for threading one's way around the rocky bits.

For OEI - until one has a goodly speed margin and terrain is no longer a concern - more than 15 degrees is, in this ops engineer's view .. a tad silly.

[rudderrudderrat]

Hi John,
For OEI - until one has a goodly speed margin and terrain is no longer a concern - more than 15 degrees is, in this ops engineer's view .. a tad silly.
It depends. I would agree if the aircraft was flying below the min maneuver speed for the configuration. However some places such as Ajaccio (LFKJ/AJA) departing RWY 02 require a bank angle of 20° and a maximum speed of 158 kts during the early Left turn - and terrain is definitely a concern.

[underfire]

It is up to the individual airline to calc EO Dep, and not all of them do it the same way, especially when it comes to adding a turn into the mix. Each aircaft has its own quirks and limitations.

I have seen calcs to max bank angle that did not take into account any course correction while in the turn...and of course, the real voodoo in the mix, the winds.

There is no public criteria that defines how to do this, nor sets any parameters for each of the variables. It is blind, basically, it states, when you ask for DEP clearance, you are telling me that your aircraft meets the min requirements on the chart or the standard climb gradient. I am not going to tell you how to get there, you told me you could do it.

If there is a turn, there is a containment area associated with that, bank limiting and turn radius keep you in the containment area.

EO is an emergency, and is treated as such in the criteria. Just becuase there is an EO SID, doesnt mean you can use it.
From FAA:

http://www.aci-na.org/sites/default/files/dermody_aci-ops-tech-conf_-_oei_surface_-_4-17-12.pdf

One Engine Inoperative (OEI) Description
• Air Carriers are required to clear obstacles in one-engine out departure situation
• Each carrier maintains their own chart of critical obstacle height & locations
• Each carrier computes a 35 ft. obstacle clearance based on specific aircraft load and
performance – given reduced climb gradient
•FAA historically only protected for instrument approach procedures
• There are known impacts to departure payload due to obstacles in departure area

[john_tullamarine]

I would agree if the aircraft was flying below the min maneuver speed for the configuration.

If we are looking at the takeoff, we are looking at whatever AFM V2 schedules are available. Min manoeuvre is not relevant for the initial terrain consideration in the event that OEI actually prevails ? No reason why the OEM can't schedule more than minimal data but someone has to pony up the ante to obtain it ..

some places .. require a bank angle of 20° and a maximum speed of 158 kts during the early Left turn - and terrain is definitely a concern.

Providing the regulatory approval is obtainable and the weight penalty can be tolerated, that's fine. If turn radius is critical one sometimes is constrained with available options.

.. not all of them do it the same way, especially when it comes to adding a turn into the mix.

True .. but, for critical runways, generally the options may dictate a very similar strategy.

Each aircaft has its own quirks and limitations.

Waffle. The numbers will vary a little but a twin is a twin and goes like a twin at commercial weights .. triples and quads in a similar vein.

.. the real voodoo in the mix, the winds.

If one fails to take account of boundary consideration winds for the escape ... turns or no turns ... one is foolish

There is no public criteria that defines how to do this, nor sets any parameters for each of the variables.

Nonsense. The AFM provides plenty of guidance in the way of examples or other OEM data is available to achieve the same end. In any case, even the most bog rat of ops engineers can do the basics just fine.

I am not going to tell you how to get there, you told me you could do it.

The operator should have scheduled appropriate data in the way of RTOW charts or similar. If a SID is not achievable OEI then the operator should have scheduled an alternative procedure. There ought to be nothing in the way of hit and miss with weights and tracking intentions.

If there is a turn, there is a containment area associated with that, bank limiting and turn radius keep you in the containment area.

Cart before the horse. The terrain analysis defines the required track details. That defines turn details. Required radius defines speed and, to a small extent, bank angle variation.

EO is an emergency, and is treated as such in the criteria.

Nonsense. EVERY takeoff is predicated on OEI for a heavy aircraft. The fact that the great majority of departures don't see a failure is a benefit to the crew's sweat index .. but the bean counters don't get any credit for that fact in regard to RTOW.

Just becuase there is an EO SID, doesnt mean you can use it.

Depends on what the operator has scheduled ..

[The ACI link doesn't appear to function .. perhaps you can revisit ?]

There are known impacts to departure payload due to obstacles in departure area

That's quite profound ..

[vapilot2004]

However, AFM/regulatory OEI limit generally is 15 degrees due to climb degradation. Company procedures may reduce this for specific escapes generally to constrain turn radius for threading one's way around the rocky bits.

Ah so, there is a track consideration, but not regulatory in nature - more cautionary on the part of the company flight procedures group.

For OEI - until one has a goodly speed margin and terrain is no longer a concern - more than 15 degrees is, in this ops engineer's view .. a tad silly.

Agreed, Sir John.

[john_tullamarine]

there is a track consideration, but not regulatory in nature

Regulations (pertinent to the jurisdiction) come into play and dictate minimum terrain clearance requirements within defined splays which, in execution, involves the hills, valleys and where the aircraft might seek to track .. just how the detail might be achieved, though, lies within the province of the operator's in house or contracted ops engineering folk. Nothing terribly difficult there .. but it does require good housekeeping and attention to detail.

It is worth keeping in mind that regulations are ALWAYS a minimum standard, whether that be design or operations ...

Given that regulations are minimum standards, the more stringent consideration should always be that of corporate governance and risk management. One might like to think that an operator seeks to operate to a standard somewhat higher than the minimum regulated.

At the end of the day, given that getting this stuff very wrong may/will have very public consequences .. simple commercial longevity suggests it ought to be of some importance within the corridors of corporate power ..

[BOAC]

The unusually inquisitive OP appears to have fainted away and has not answered my query. 'Tas happened before too.

[aimingpoint]

More than 15 degree you lose CLB PERF, that is preset for each segment of takeoff.

[latetonite]

And why, would I, im my specific plane, on any specific day, have to limit my bank angle to 15 degrees? Do you know my performance?

[john_tullamarine]

Several considerations ..

A specific bank angle - not necessarily 15 deg -

(a) stall margins ref IAS and stall speed - configuration
(b) turn radius for obstacle or airspace avoidance - ref speed

and, for OEI, generally a maximum of 15 deg -

(c) degradation of an already shallow climb gradient

[Capn Bloggs]

An example of Bank Angle effect on performance:

http://i521.photobucket.com/albums/w334/capnbloggs/Gradlossinturn.jpg (http://s521.photobucket.com/user/capnbloggs/media/Gradlossinturn.jpg.html)

[latetonite]

Thanks,Bloggs, but I am aware of performance limitations.

While a SID gives me lateral and horizontal restrictions, even noise abatement procedures for that matter, I do not understand why ATC wants to tell me how I steer the airplane in order to comply with their requirements.

[CL300]

To my knowledge, except on TERPS, where on normal departure you have 0.8% margin on the said departure ( besides ATC constraints or specific airports location); since PAN-OPS 2 and above there is no provisions for OEI departure. SID are just airspace 3D tracks with a minimum performance designed in them.

If an airplane loses an engine, then, the operator has to provide an acceptable alternative option, and this for every take off, every weight, every intersection of every airport intended to be used. This track can well be the opposite of the normal departure ( i.e. GVA Left turn in OEI instead of Right Turn for SID).

As far as eu-ops is concerned, no turn are allowed below 50ft, between 50 ft and 200ft max bank to 15° up to 400ft max bank 20° up to 1500ft max 30° If banking more than 15° obstacle clearance goes to 50 ft vertically. Again some airport designs ( AJA/GRZ/...) might require something different, but it is definitely not something that the PIC choose at the last minute. :cool:

In FAA land, the distance increases with distance 48ft/Nm....0,8%....

This is from memory... so..

[john_tullamarine]

As far as eu-ops is concerned,

I don't claim specific EASA expertise .. I presume your comments relate only to AEO ? For instance, I would expect OEI turn clearance to be 50ft regardless .. ?

[CL300]

OEI.. not AEO..

as per regulation ( the way i read it ) if bank angle is less than 15° then clearance is the standard 35 ft...
This means that on the first 200ft vertically, from 35ft, you can have as little as 35 ft of clearance for Close in obstacle... When you start to breathe again :} ; ones can start maneuvering and have a beautiful 50 ft. ( as a minimum)

no ? :uhoh:

[RAT 5]

you can have as little as 35 ft of clearance for Close in obstacle... When you start to breathe again

A miss is a good as a mile.

[john_tullamarine]

as per regulation ( the way i read it ) if bank angle is less than 15° then clearance is the standard 35 ft...

Can you cite the specific regulation for us please ?

you can have as little as 35 ft of clearance for Close in obstacle

Not quite the case although it reads nicely ... gross to net margin means that, from the end of the first segment (should that exist) the calculated net clearance may be 35ft .. but the actually expected calculated clearance will continually increase as the takeoff progresses ...

A miss is a good as a mile.

Perhaps .. but as one gets older, the comfort factor kicks in ...

[Mach E Avelli]

Summarizing one country's clearly written Part 121 (obviously not Australia!).


Straight flight path: fly V2, clear obstacles by 35 ft


Up to a 15 degree change from runway alignment: as above


Beyond a 15 degree change from runway alignment: turn may commence not below 50 ft above obstacle (which could be the runway surface if there are no obstacles, my comment) - AND provided bank angle does not exceed 15 degrees, no correction to V2 or AFM OEI climb gradient - clear all obstacles by 50 ft while turning


Bank angles in excess of 15 degrees: no turn below 50 ft above obstacle - apply additives to V2 and reductions to AFM OEI climb gradients - clear all obstacles by 50 ft (a simple table of corrections is supplied in the rules)


Not wishing to insult the intelligence of those many Ppruners on this site who are clearly experts in various matters....BUT, none of the above should be confused with SIDS, which assume all engines operating, speeds comfortably above V2 and typical bank angles of 25 degrees. The OEI path could be in quite the opposite direction to that required by the SID. From reading some of the foregoing, I think a few here may be confusing the two.

[CL300]

Eu-Ops 1.495... I believe...

[john_tullamarine]

Putting aside minor variations, what is the approach adopted for numerical analysis in the case of OEI bank angles greater than 15 deg ? NFP at commerical weights is going to be negative and to address this at light weights is going to make critical takeoffs somewhat non-viable ?

[Mach E Avelli]

Yes, probably sufficiently non viable that most operators will opt for 15 degrees only, unless the terrain is really tricky (PNG, Peru?). From NZ Part 121:




BANK ANGLE SPEED GRADIENT


15° to 19° V2 1 x Aeroplane flight manual 15° gradient loss

20° to 24° V2 + 5 knots 2 x Aeroplane flight manual 15° gradient loss

25° V2 + 19 knots 3 x Aeroplane flight manual 15° gradient loss

[john_tullamarine]

Interesting .. but I think I would be seeking to organise a more usefully accurate penalty via concession .. that's a bit broad brush for me.