Landing gear down and segments?

[Beirut pilot]

Hi pprune!
A young soul here seeking clarification regarding aircraft performance...
When you depart on hot days, and when you keep your landing gear down to cool down, how do you do with the 2nd segment? Is that segment, during performance calculations, delayed? And if so, is that a separate calculation?
If i recall correctly, first segment ends when landing gear is fully retracted and all you have to take into consideration is a positive rate of climb (for a two engine)? In some airports obstacles are very close...My question is how those should be cleared when all you have to do is having a positive rate of climb (instead of, during 2nd segment, 2.4% gross and 1.6% net)?

I might just be young and stupid though...But i do believe in the power behind the question ''why?''.

Thanks!

[skyhighfallguy]

interesting point

second segment climb is really important if you have an engine failure.

and there are some times where there are so many obstacles nearby you would want to know the performance

BUT, I think most of us would take off and not retract the gear if you wanted to cool the brakes a bit

BUT if one of the engines quit, then we would retract the gear for performance.

It is pretty rare these days to leave the gear down to cool the brakes, the only time I can think one would do this is if you were in the traffic pattern doing multiple take offs and landings as in a training situation

[Microburst2002]

Second segment is purely a one-engine-inoperative thing.

It doesn't exist in an all-engine-operating situation.

[Beirut pilot]

Thanks SHFG for that quick response!
If you would retract the gear for performance reasons then you should know the exact point were the obstacles are?
I mean say for ex. that after takeoff from RWY 10 the first (and most limited) obstacle are approx 11ft, 200m from the end of TODA... (11ft/(200/.3048)*100)
That will give you a climb gradient of 1.6764% NET (or 2.4764% GROSS)...
With landing gear down...Can you really clear that obstacle?

Again, i'm more than thankful for your response SHFG, and i will follow this thread with curiosity!

[john_tullamarine]

Some AFMs or related operational documents will give you data for the consideration.

However, one needs to keep in mind that, if you do your own thing .. you may be called to justify it subsequent to a mishap or other conflict.

Doing the occasional non-standard operation with requirements to do further actions in the event of this and that .. might be setting yourself up for a surprise. I'm sure most of us can recall the odd time the gear has been overlooked for whatever reason and not picked up until after takeoff scan time .. ?

Generally only a concern if you are using very heavy braking .. eg accel stop testing or similar .. when leaving the gear down is the technique used to manage the heat buildup problem.

Another approach is to retract the gear, get a suitable amount of air underneath you and then extend it to address your concerns without terrain worries.

[perantau]

Engine failure at or soon after V1. If the engine quits after getting airbourne, probably have cleared the DER by more than 35ft.

[cosmo kramer]

Hi Beirut pilot

It's common that certification requirements are being mixed up with procedural requirements. I am kind of a geek when it comes to this topic, so a rather long reply follows...


Certification requirements:

The different segments, and corresponding gradients, of a take off are certification requirements (FAR 25). Hence, the manufacturer of your aircraft has to demonstrate that your aircraft will met these requirements or your aircraft would never have been allowed to fly.

These are just ways for the authorities to ensure, that the aircraft being certified, is able to get away from the ground somewhat at all. They (FAA originally) deviced these manoeuvres and set the requirements, that needs to be demonstrated, to a level that they decided was to be considered safe.

It has nothing to do with obstacle clearance. They demonstrate that the aircraft has a certain climb performance, nothing more, nothing less!


Procedural requirements:

A complete different authority (ICAO), set a limit for minimum obstacle clearance during (all engines operating/normal/standard/day-to-day) takeoffs. This is described in ICAO Doc 8168: Procedures for Air Navigation Services (PANS OPS), currently 5th edition.

Their assessment of what is safe resulted in a minimum required gradient of 3.3%. For our modern high-performance aircrafts with gradients in the 15%+ range, this is not a problem (remember these requirements were set in the 60'ies and applies to propeller/general aviation aircrafts as well).

What further adds to the confusion, is that previous versions (up to 3rd edition), there was indeed a level segment for acceleration in PANS OPS procedure design. This was because Lockheed Constellations, DC-3s etc. didn't have all that great performance. But still it's shouldn't be confused with the certification requirements in FAR25. A level segment for acceleration is obsolete since 1993 with the 4th edition of PANS OPS.

In short, so even with gear-down and accelerating, your modern aircraft should have a gradient well above 3.3% :ok:


Engine failure:

ICAO procedures (PANS-OPS/Doc 8168) are ALWAYS assuming all engines operating:

http://s3.postimg.org/pjj8upkxv/image.jpg

So if your engine subsequently fails, your brake cooling becomes a secondary issue and you retract the gear. There after you "apply the note", in the quote above = follow the engine failure procedure established by your operator: You and your company are on your own! It's YOUR responsibility to clear obstacles and no agency is guaranteeing you anything.

P.s.
For go-around the same misconceptions exists. The reply above is partly copied from a recent reply I made to that topic in http://www.pprune.org/tech-log/557338-missed-approach-procedure-baesd-what-performance-2.html . Maybe it will interest you to read my replies there too.

[Beirut pilot]

Thank you all for your inputs, especially Cosmo for your detailed answer. I will go through it once again soon, and if i encounter any question i will simply ask here.

[Wizofoz]

It is it actually a published procedure on your type to leave the gear down to cool the brakes, or just something someone thought of?

If we depart and leave the gear down on the 777, we have specific performance data for that configuration.

If it's actually a certified procedure on your aircraft, the performance data should also be published.

It would not be safe to simply decided to raise the gear in response to an engine failure, as you would have already lost performance, and gear retraction is often a high drag sequence.

[Microburst2002]

In some airplanes you can get an ECAM prompting you to keep the gear down, but in IMC in high elevation field, high temperature, max weight and high surrounding terrain… Could be a bad thing. Also, you may consider following the engine out procedure. That should keep u safe.

In VMC, terrain in sight, you can go on according to what you see. Probably doing well most of the times.

[Beirut pilot]

It would not be safe to simply decided to raise the gear in response to an engine failure, as you would have already lost performance, and gear retraction is often a high drag sequence.

Couldn't agree more...

In VMC, terrain in sight, you can go on according to what you see. Probably doing well most of the times.

Even if there are no guarantee for anything to work at 100%, it would just be strange to go on ''probability''...Especially when aircraft performance, in other cases, are so detailed and safety oriented.

On the other hand...

As stated above by Wizofoz, there seem to be some sort of tables for that very special config. Now i want to know how common those tables are? Just curious.

[Microburst2002]

Well, some manufacturers give that info, others don't, which I take as the L/G DOWN performance not being required by any certification or operation regulations.

Basically you are on your own. My opinion is that there is no problem whatsoever unless you are in a challenging airfield, like I mentioned (BOG in a hot day and the airplane full to the brim). In that case I would feel scared and I would try to stay in the lower terrain area, climbing like a vulture if need be. For that, a special engine out procedure is as adequate as any other option (like visually climbing like a vulture).

In non challenging airports I wouldn't care much, my airplane climbs like a rocket with two engines.

[latetonite]

If my airplane, on two engines, would be unsafe to fly with the gear down, regarding obstacles, I would also not attempt this departure with the gear up.

[john_tullamarine]

They (FAA originally) deviced these manoeuvres and set the requirements

Not quite right.

The original story for the current performance philosophy/requirements is the ICAO Final Report of the Standing Committee on Performance dating back to 1953. One of our posters, a long time colleague and very kindly, passed his personal copy onto me some time ago .. now a valued reference library document on the bookshelf to my side.

Various States then publish their implementation (evolving over the years) of these requirements. Hence we see FAR 23/25 etc.


It has nothing to do with obstacle clearance. They demonstrate that the aircraft has a certain climb performance, nothing more, nothing less!

Not quite right.

(a) you are talking about WAT limits .. which are included in the AFM and represent the Design Standards bottom climb line. Rarely are these the critical path for a takeoff weight calculation in the field. Usually, either runway length or obstacle clearance is more critical.

(b) you are overlooking segment obstacle clearance .. which also is included in the AFM and must be met at planning to establish RTOW compliance.


A complete different authority (ICAO), set a limit for minimum obstacle clearance

Not quite right.

PANS/OPS relates to routine AEO operations, letdowns, etc. Nothing to do with takeoff calculations which are AFM based and OEI.


In short, so even with gear-down and accelerating, your modern aircraft should have a gradient well above 3.3%

Now that depends entirely on the gross weight and how the aircraft is being operated .. a very long bow to draw, methinks.


In VMC, terrain in sight, you can go on according to what you see.

Danger, Will Robinson ...

OEI, the gradients can be so shallow that they defy any perceptual attempt to wing it on the day.

Either you have done the sums and fly to the procedure .. or you are in the lap of the Gods .. and the Gods, generally, don't care a fig, ergo, a high probability of a subsequent CFIT.

Some States have permitted this sort of thing for smaller heavy aircraft .. eg, Australia for under 50,000lb permitted reduced splays in VMC (to allow the F27 some flexibility in the early days). Interestingly, this was metricated to 20T (if the memory serves me correctly) .. which thwarted the original rationale. I protested formally (long ago) and gave up in the face of the usual opposition. I notice that it now has sneaked back up to 22.7T ...

Main concern is that it just is NOT feasible to wing OEI obstacle clearance visually ... requires visual/perceptual discrimination beyond our capability.

[skyhighfallguy]

dear OP


imagine you are taking off and your landing gear fails to retract

do you: stop, and look at data

or

DO YOU FLY THE PLANE?

It would be really rare, though not impossible, to have landing gear fail to retract and also lose an engine at the same time, so you will probably get away with it.


Now, it may interest you to know there are 4 segments of climb and it is not just about losing an engine.

IN REAL LIFE big airlines have engineering departments that make all sorts of calculations for each airport and each runway so we really don't worry about it too much.


But if we had a takeoff from a non routine airport, we would have to examine things.

Pilots sometime have to just "wing it" or play it by ear.

Flying is an art as well as a science!

[Rick777]

The bottom line is that any pilot worthy of the name would not take off with brakes so hot that the gear need to stay down for cooling if there was any question about climb performance.
Also if you were so heavy you need to worry about second segment climb you would also have to worry about stopping ability with those hot brakes. Academic discussions are fine, but in the real world you need to be a pilot.

[john_tullamarine]

Pilots sometime have to just "wing it" or play it by ear.

Some of us might opine that planning and knowledge is superior ...

Also if you were so heavy you need to worry about second segment climb you would also have to worry about stopping ability with those hot brakes

That doesn't necessarily follow at all .. perhaps you might elaborate for us ?

[Wizofoz]

My point to the OP was that he stated When you depart on hot days, and when you keep your landing gear down to cool down, as if it is a generally accepted procedure.

I have operated in some very hot places, and have never heard of this being a common practice. It is included in (as an example) the 777 as a non-normal, but i for one have never actually used it , or know of anyone who has.

So to ask again to Beriuit Pilot, is this idea actually included in your manuals, is performance information available, and what information would trigger you thinking it was necessary on any particular day? People will often end up operating in a particular way because :So-an-so told me too", without it actually being a procedure designed for or approved by the manufacturer.

[Stone_cold]

Further to the Wiz :

It is usually detailed in the MEL OPS proc for Main gear inop( Airbus) . It indicates that specific Perf has to be done . Also mentions "in case of engine failure case .

Doesn't seem to be any reference for the test pilots to just leave them hanging because they cooked the brakes or its a " hot " day . Never seen this considered even in a region where OAT's reach high 45+ degrees in the summer . If brakes hot " delay takeoff " . Seems clear from the manufacturer's viewpoint .

[cosmo kramer]

The original story for the current performance philosophy/requirements is the ICAO Final Report of the Standing Committee on Performance dating back to 1953. One of our posters, a long time colleague and very kindly, passed his personal copy onto me some time ago .. now a valued reference library document on the bookshelf to my side.

Various States then publish their implementation (evolving over the years) of these requirements. Hence we see FAR 23/25 etc.

The point was that the rest of the world pretty much adopted the US certification specifications (in Euroland now CS25 as an example). Still, thank you for that information about the origins of the FARs.

It has nothing to do with obstacle clearance. They demonstrate that the aircraft has a certain climb performance, nothing more, nothing less!

Not quite right.
(b) you are overlooking segment obstacle clearance .. which also is included in the AFM and must be met at planning to establish RTOW compliance.

We have to differentiate between normal ops and engine out scenario. Our take off calculations are taking into account engine out.

For a normal take off (with gear down as the example of the original poster), segment compliance is absolutely not an issue, nor a requirement. In fact there are no segments in a normal takeoff. What you have to comply with during a normal takeoff is the procedural climb gradient. See below...

A complete different authority (ICAO), set a limit for minimum obstacle clearance

Not quite right.

PANS/OPS relates to routine AEO operations, letdowns, etc. Nothing to do with takeoff calculations which are AFM based and OEI.

To be more accurate:
A complete different authority (ICAO), set a limit for minimum PROCEDURAL obstacle clearance (standard and minimum 3.3%).

I.e., they set the standards for what they considered to be a safe clearance of obstacles for design of instrument procedures.

And... EXACTLY... they have nothing to do with an engine out scenario. See above...

In short, so even with gear-down and accelerating, your modern aircraft should have a gradient well above 3.3%

Now that depends entirely on the gross weight and how the aircraft is being operated .. a very long bow to draw, methinks.
Think about it again: An aircraft that does 15-20% climb gradient all engines operating, will have no problems making a 3.3% gradient with the gear extended.

[cosmo kramer]

latetonite:
If my airplane, on two engines, would be unsafe to fly with the gear down, regarding obstacles, I would also not attempt this departure with the gear up.
My friend latetonite, always manage to say what I mean in A LOT fewer words. :}

[cosmo kramer]

It would not be safe to simply decided to raise the gear in response to an engine failure, as you would have already lost performance, and gear retraction is often a high drag sequence.

Ahhh, I'm confused now. :confused:

Gear is ALWAYS raised in a response to an engine failure. That is what the first segment is there for.

Takeoff calculations only deal with engine failures at ONE specific point in time: V1.

If your engine fails before V1, you stop obviously. If it happens AFTER V1, you have gained performance - not lost performance.

If my engine fails at 200 feet altitude, I had 200 feet more altitude gain with all engines operating. If I forgot to retract the gear for some reason, obviously I would do it at this point to prevent carrying a loss of performance further into the departure (now my engine failure contingency procedure, not the SID).

[skyhighfallguy]

tullamarine


I said play it by ear and I meant it. So, here you go. YOU takeoff in a twinjet and both an engine failure happens and you happened to forget to remove the gear pins and YOU CANNOT retract the gear.

Do you open up your emergency checklist and follow the ENGINE OUT GEAR UNABLE TO RETRACT PROCEDURE ...TAKEOFF

(lots of luck)

Or do you figure something out right away?


Beirut pilot. I have a feeling you think we keep the gear down to cool things off all the time. Like I mentioned, if you were in the pattern doing multiple landings, full stop with brakes as in a training situation, even DP Davies, the brilliant author of "HANDLING THE BIG JETS" indicates you might keep the gear down to cool it off in the traffic pattern.

But as others have indicated, you wouldn't leave the gate, or the ground if you knew the brakes were "TOO HOT"".

IF you had rejected a takeoff and the brakes were HOT, there is a brake cooling schedule provided to the pilot to allow the brakes to cool down PRIOR to another takeoff attempt. THE idea is that on the next takeoff attempt you might have to REJECT that takeoff too. And you need the brakes cool in order to achieve stopping distance. Some types of brakes are less in need of cooling, but that is each type of plane to consider and not a generality.

So, again, we rarely if ever do what you think we do. Training is the only situation you might consider to leave the gear down (mind you, if there is an overheat or fire in the wheel well you might need to lower the gear, but that is a different animal)>


good luck

[john_tullamarine]

It is usually detailed in the MEL OPS proc for Main gear inop( Airbus) . It indicates that specific Perf has to be done

A most important point. MEL applies to INTENTIONAL operation with a U/S.

The Design Standards still must be observed, hence most MELs include additional restrictions to address whatever the U/S might compromise in the way of the Standards.

In this case, performance still requires OEI segment capability .. hence the usual significant weight delta.


Doesn't seem to be any reference for the test pilots to just leave them hanging because they cooked the brakes

A specific FT consideration when playing with accel stop activities. Not relevant to routine line operations.


The point was that the rest of the world pretty much adopted the US certification specifications

.. but with significant differences in philosophy as becomes clear should you read and compare.


Our take off calculations are taking into account engine out

Precisely .. and that ALWAYS includes OEI segmented obstacle clearance considerations.


For a normal take off (with gear down as the example of the original poster), segment compliance is absolutely not an issue, nor a requirement.

Absolutely not so.

Should you INTEND to leave the gear down - doesn't matter what the reason might be - then the operation falls into the realm of MEL considerations. One MUST incorporate a weight penalty, and whatever else may be relevant to the Type, to address the normal OEI segmented takeoff exercise .. this time around, with the gear down.

The AFM defines what a normal takeoff might be, not the pilot on the day.


there are no segments in a normal takeoff

Again, not so. The AFM defines how you should be conducting the actual takeoff for whichever of AEO and OEI applies on the day .. recalling that any given takeoff will involve one or both ... Both are considered as an each time exercise and one or the other will dictate the limiting case for the RTOW calculation.

The overall inference, of course, is that the AEO procedure keeps the aircraft flight path above the OEI gross path.


they set the standards for what they considered to be a safe clearance of obstacles for design of instrument procedures.

.. and of no relevance to takeoff ..


An aircraft that does 15-20% climb gradient all engines operating, will have no problems making a 3.3% gradient with the gear extended.

Providing that the handling procedure is appropriate .. but of no relevance for OEI considerations.


Takeoff calculations only deal with engine failures at ONE specific point in time: V1

.. for the AFM calculation. The inferred responsibility on the operator/pilot is that the aircraft, AEO, will be operated in a manner which doesn't compromise a post-V1 failure. This can get a bit complicated if the takeoff requires turn(s).

The operator/pilot is responsible for making sure that the takeoff can get to an appropriate terrain clear point for a failure at any point during the process ..


YOU takeoff in a twinjet and both an engine failure happens and you happened to forget to remove the gear pins and YOU CANNOT retract the gear.

Fortunately, I haven't been in that situation ... although a mate was years ago on the F27 .. didn't seem to hurt his career as he ended up a successful and, by all accounts, a good checkie.

Seriously, though ..

(a) the Design Standards don't have regard to incompetence

(b) .. nor multiple significant failures

In the situation you posit .. the pilot could be in really serious strife, depending on the nature of the aerodrome on the day.


Or do you figure something out right away?

I suggest that most competent commanders will have armchaired that sort of scenario (gear retract failure) and have at least a generic plan. For difficult terrain runways in a commercially rational world .. there are some situations which are best handled by not getting out of bed that morning ...

[cosmo kramer]

they set the standards for what they considered to be a safe clearance of obstacles for design of instrument procedures.

.. and of no relevance to takeoff ..

Excuse me... this is of HIGH relevance to the all engines operating takeoff.

This example won't kill you, if you do not comply, but will get you into trouble with the air traffic controller.

Replace "due to airspace structure" with "due to mountain in departure path", and you get into more serious trouble. And it might not even limit you in your takeoff (engine out) calculations, as the SID might take you OVER the mountain and your engine failure procedure might take you in another direction with no significant obstacles.

In the example of Cologne, you have 3815 meter (12516 feet) runway. SO your takeoff performance calculations might give a result with so much derate/assumed temperature thrust reduction, that you are unable to met the 15.2% climb requirement for all engines operating.

This is from experience, not assumption. In this case you have to select MORE thrust to comply with the SID, than required for the engine out procedure. Your performance calculations won't warn you of this, as the software doesn't get any information about what SID you intend to fly.

So YES the procedure gradient is of HIGH importance to your all engines operating takeoff.

Here is the example:
http://s12.postimg.org/om0vln3jh/Screen_Shot_2015_06_22_at_16_47_27.png

http://s1.postimg.org/3q6fr9j9b/Screen_Shot_2015_06_22_at_17_01_43.png

[john_tullamarine]

this is of HIGH relevance to the all engines operating takeoff.

You are mixing two concerns. First, the takeoff bit and then the subsequent departure. Both need to be considered and the more critical determines the final departure weight.


unable to met the 15.2% climb requirement for all engines operating.

Again, not relevant to the actual takeoff calculations but may become the critical path for final weight figures. The two must be treated separately and then the more restrictive becomes the critical figure. Not philosophically different to the case where, say, the enroute cruise OEI weight limit to clear the mountain range restricts departure weight below the RTOW.

[Microburst2002]

An old pirate theory goes that an obstacle that you can see is not an obstacle.

Of course that is nonsense, but in the case of a L/G down departure, I think you will be able to assess very clearly if you have a problem or not.

But, both the L/G down and an engine failure on top of that? Wow, that's not your day! there is a procedure for that, though:

FINGERS………CROSS

Personally I don't know what I would do. In my airplane, avoid obstacles visually, if in IMC go for the EOSID and pray, or "fly the black", or try to return overhead the airfield, although such turn would kill most of my climb ability…

FINGERS……..CHECK CROSSED
:{

[cosmo kramer]

You are mixing two concerns. First, the takeoff bit and then the subsequent departure. Both need to be considered and the more critical determines the final departure weight.

I actually believe YOU are the one mixing things up. I don't know why you want to talk about preflight planning.

I am talking about the ACTUAL takeoff. In 99.999% of the cases you are NOT going to be experiencing an engine failure (for which your takeoff performance calculations have been made).

So your takeoff will not be a "takeoff bit"... it will ONLY be the departure, as long as your engine doesn't fail.

The "takeoff bit" will only be relevant if your engine fails. It's a purely hypothetic "what-if" calculation. The ACTUAL departure is very real - every time.

P.s.
...it's funny that you say I am mixing things up, when I started out in the first post to say that It's common that certification requirements are being mixed up with procedural requirements.
And I there after split the post in bold sections.

Facts are:

- You can safely takeoff with gear extended (except in cases like Cologne NOR8F, with an extreme procedural gradient requirement).

- You do not need to apply MEL for flying with gear extended, if retraction is operable.

- It will have no impact on your takeoff performance calculations and doesn't need to be accounted for (as you can retract the gear if necessary)

- If an engine fails, you retract the gear as usual.

End of story.

[john_tullamarine]

I think that we should just agree to disagree, perhaps .. ?

[cosmo kramer]

I am not a fan of that concept. I prefer the topic discussed to the end, where everyone agrees.

Why should I operate according to MEL for gear U/S, just because I delay retraction?

Rhetorical question:
In the example of NOR8F, I have to delay flap retraction to 4000 feet as well, as I can't afford to accelerate if I want to comply with the altitude restriction at 4.8 NM KBO VOR. Engine failure procedure will have me retracting them at 1900 feet (1500 feet AGL). Should I in this case check the MEL for restrictions for flying with flaps U/S?

Obviously not. Why should it be different for the landing gear?

The AFM defines what a normal takeoff might be, not the pilot on the day.
Wrong, the pilot operating the aircraft needs to be flexible, and make sure to comply with the challenges of each individual departure. For that, the performance manual is a tool to support the pilot in making good decisions.

[john_tullamarine]

OK, let's continue with the discussion ..


Why should I operate according to MEL for gear U/S, just because I delay retraction?

What does your AFM say in respect of selection of gear during the takeoff ? Commonly something along the lines of "retract gear three seconds after liftoff .. ?"

If the pilot wishes to operate in a manner significantly different to that specified in the AFM, which may/will compromise the certification basis, then one needs to consider what answers the pilot might have to questions at the Enquiry after the mishap .. regardless of whether the point in question has any relevance to the mishap.

No different to, say, using a non-AFM flap setting for takeoff .. eg nil flap on light twins .. which I routinely did in the past. For the twins I routinely flew, I had done sufficient climb testing to provide me with the basis for the variation and, more importantly, the basis for an argument in court.

In essence .. in the absence of an abnormal/emergency, either you do

(a) sufficient certification work to establish compliance and a defence at law or

(b) follow the AFM or

(c) use the MEL as your get-out-of-jail-free card

Just to say that you will do what you want to do today because you are the pilot is a rather reckless approach to risk management, I suggest.


I have to delay flap retraction to 4000 feet ... Engine failure procedure will have me retracting them at 1900 feet (1500 feet AGL). Should I in this case check the MEL for restrictions for flying with flaps U/S?

A facile argument. The takeoff will (or should) have been predicated on

(a) the AEO requirements, AND

(b) the OEI escape as appropriate.

A pilot (generally not the reputable airlines) without benefit of a rigorous ops engineering department takeoff procedure in support who departs without an AEO to OEI transition plan to cover all eventualities eventually may not have a good day .... He/she certainly won't have an easy time of a subsequent Enquiry.


the performance manual is a tool to support the pilot in making good decisions.

No. The performance data is to provide the pilot with information to permit compliance with the rulebook. The pilot should be making sensible decisions within the parameters of those requirements for other than emergency situations beyond the normally expected planning regime.

Alternatively, one could pose the question .. how does the pilot, in the situation you posit, make good decisions whilst winging it on the fly ? I put to you that a good decision requires both a successful outcome (in respect of the decision process) and a defensible logic .. the latter including compliance with the Design and Operating Standards where operations, essentially, are normal.

[cosmo kramer]

What does your AFM say in respect of selection of gear during the takeoff ? Commonly something along the lines of "retract gear three seconds after liftoff .. ?"
Boeing FCTM:
"Retract the landing gear AFTER a positive rate of climb is indicated on the altimeter."
It doesn't say how long after, just that you obviously shouldn't do it BEFORE positive rate of climb.

If the pilot wishes to operate in a manner significantly different to that specified in the AFM, which may/will compromise the certification basis
The aircraft is (obviously) certified to takeoff, fly and land with gear down.

I have to delay flap retraction to 4000 feet ... Engine failure procedure will have me retracting them at 1900 feet (1500 feet AGL). Should I in this case check the MEL for restrictions for flying with flaps U/S?

A facile argument. The takeoff will (or should) have been predicated on

(a) the AEO requirements, AND

(b) the OEI escape as appropriate.
You are contradicting yourself.

So in the flaps example:

(a) Is ok to check that I can takeoff with flaps extended and keeping them extended to 4000 feet in AEO, AND

(b) in case of OEI, I have checked that the flaps need to be retracted earlier (at 1900 feet).


In the case of the gear extended I can do exactly the same checks!:

(a) AEO/gear down, I met any procedural gradients required in my SID (usually 3.3 percent), AND

(b) in case of OEI, I have checked that the gear needs to be retracted earlier (after liftoff and positive rate of climb or when an engine fails, whichever is later).

Alternatively, one could pose the question .. how does the pilot, in the situation you posit, make good decisions whilst winging it on the fly ?
In the situation described, nothing is being winged on the fly. Both cases have been duly accounted for.


...the basis for an argument in court...
...your get-out-of-jail-free card...
...He/she certainly won't have an easy time of a subsequent Enquiry....
In the civilised world, I can only think of a few examples of any pilot having to go to court (usually acts of gross negligence - like e.g. Hapag-Lloyd Flight 3378).
Most incident investigations are there to help the pilots! And to understand and learn from what happened.

Yet I hear this kind of argument often. I NEVER worry about having to go to jail (let alone court), when doing my work as I never do acts of gross negligence.
Maybe something to think of, so we can stop this kind of argumentation.

[cosmo kramer]

Boeing 737 FCTM:
Touch and Go Landing - General

Accomplish the pattern and approach procedures as illustrated. The landing gear may remain extended throughout the maneuver for brake cooling, but be prepared to retract the landing gear if an actual engine failure occurs during go-around.
Are you saying what Boeing recommends is reckless and violates certification data?

Do you think the aircraft "knows" the difference between if it's doing a takeoff or doing patterns?

[Gysbreght]

If I may be permitted to add a few observations to the discussion:

A distinction needs to be made between limitations and procedures.

“The aircraft is (obviously) certified to takeoff, fly and land with gear down.”

That is a somewhat simplistic statement. The aircraft is certified for operation within the limitations stated in the Airplane Flight Manual (AFM). The AFM states that the weight that achieves the minimum climb gradients for altitude and temperature (WAT limit), and allows takeoff within the available lengths of runway, is an operating limitation.

In addition, there are usually operating rules, for example FAR parts 91 and 121. FAR 121 adds the requirement that the takeoff weight must permit a net flightpath that clears obstacles by the required margins.

Although most performance limitations are based on a scenario of engine failure, it is not correct to say that they are totally divorced from the performance in normal operation with all engines operating. That is perhaps somewhat beyond the scope of this forum, to understand it you have to go back to the origin in the Final Report of the SCOP that JT mentioned. Let’s just say that the certification basis assumes that the airplane will be operated by qualified pilots in accordance with the recommended procedures.

Note that all performance limitations are stated as a maximum allowable weight for the prevailing conditions. Exceeding any of those limitations is an offence against the law and may result in sanctions, irrespective of whether that exceedance is a factor in an investigation. However, any accident report that I know of, usually has a statement in one of the first sections to the effect that “the weight and loading were within limits”.

Then there are operating procedures. Operating procedures for performance are stated in the AFM in the form of ‘guidance material’, to enable the flight crew to achieve the performance assumed in the calculation of weight limitations. Deviating from those procedures is not a punishable offence, but may result in an invitation for a “tea and biscuits” with the chief pilot. If the deviation is a factor in an incident or accident, the pilot will be asked to explain why he considered it safe to deviate from the Standard Operating Procedure (SOP). If the investigation finds that explanation unsatisfactory, sanctions may follow.

Regarding flap retraction after takeoff from Cologne, my understanding is that such on operating restriction is usually complied with by maintaining a certain rate-of-climb. The acceleration remaining while maintaining that rate of climb will determine when you reach flap retraction speed. At that speed you can retract the flaps.

P.S.

Another way to put it: by delaying gear retraction, you’re reducing the performance margin that you may need in a contingency. In other words, you’re making the takeoff less safe than it could have been, unless you can show a safety benefit for delaying gear retraction.

[cosmo kramer]

Another way to put it: by delaying gear retraction, you’re reducing the performance margin that you may need in a contingency. In other words, you’re making the takeoff less safe than it could have been, unless you can show a safety benefit for delaying gear retraction.

I see what you mean, but this is a completely other discussion!! This is a discussion about safety vs. commercial considerations and efficiency. We are all allowed to have our personal opinion about that matter, but the rules are the rules.

Since NOT retracting gear has already been accounted for, the requirements for all eventualities have already been covered.

What you are saying is basically this:
If an engine fails, AND a mistake is made (like not following the engine failure contingency procedure), then the difference between having had the gear extended might get you into trouble.

That is true, but we have loads of such procedures that reduces margin. Some obvious are:
- Reduced takeoff thrust.
- Fuel tankering

There are indirect reductions in margin as well:
- Flying with a full passenger load (empty aircraft performs better).

This is such a procedure too:
- Flying with the gear extended is a commercial consideration (to reduce turnaround time).


An example to make this more palpable, 3 legs:

- You fly to Egypt with fuel tankering.
- You land at your destination with max landing weight in 45 deg C.
- You have 45 mins turnaround, and the brakes are allowed to be cooled sufficient to perform another takeoff.
- There after you fly a short 20 min to another Egyptian airport and land at max landing weight again in 45 deg C.

a) If you retract your gear during the short leg, accumulation of the heat from first and second landing will require a long brake cooling time, before you can leave again.

b) You fly with gear extended and you can make a quick turnaround between leg 2 and leg 3.


For leg 2 (the flight with gear extended), all requirements are being adhered to. All eventualities have been covered.
- The brakes were sufficient cool to reject a takeoff.
- For AEO with gear extended, I can safely follow applicable SID and adhere to the required climb gradient.
- For OEI, I can safely retract the gear and follow my contingency procedure (no need to apply MEL restrictions).
- In either case, my brakes are cool enough to allow for an immediate landing.
- If the gear is extended or not, only has a bearing on how long I have to wait before I can perform leg 3.

The above b) is a recommended procedure in my company...
Just to say that you will do what you want to do today because you are the pilot is a rather reckless approach to risk management, I suggest.
...but on the day, I decide what to do, as a captain. And I use available manuals as a tool to help manage the risk. :ok:

I am not doing anything illegal, I am not going to court or jail, and I won't be having tea and biscuits with anyone. Most likely I will be drinking my black coffee with my F/O on leg 3 back after a short turnaround. :E

P.s.
Regarding Cologne, you have to fly at V2 until reaching 4000 feet. Hence, there is no acceleration.

[Gysbreght]

What you are saying is basically this:
If an engine fails, AND a mistake is made (like not following the engine failure contingency procedure), then the difference between having had the gear extended might get you into trouble.
Contingencies are not limited to a loss of thrust on one engine. Think about the recent mishap of a Quantas A380 at Singapore, or the famous ditching of an A320 in the Hudson river. In the latter case, when the plane hit a flock of geese, a couple of 100 ft might have made the difference between being able to reach a runway or having to ditch.

You're just being stubborn.

[cosmo kramer]

or the famous ditching of an A320 in the Hudson river. In the latter case, when the plane hit a flock of geese, a couple of 100 ft might have made the difference between being able to reach a runway or having to ditch.

With 99% likelihood, US1549 departed with derate and assumed temperature thrust reduction. Had they not done so, they might have been able to make a runway instead of ditching - according to the above logic.

A reduction of takeoff thrust was obviously a reduction of margin.
Did anyone blame them?
Did anyone go to jail?

Of course not, since it's part of an acceptable risk. Anything that reduces our margin is most of the time a commercial compromise.

You're just being stubborn.
No, I agree about a reduction of margins reduce safety. Where we disagree is about acceptable level (those are set by rules and regulations).

[FE Hoppy]

Given that all the performance data published in the AFM/AOM is defined by configuration, thrust and speed I'm not sure, unless like JT you happen to have gathered certification data, how a pilot can account for a deviation from the prescribed configuration, thrust and speed without a great deal of guess work.


As for post v1 failures, I'm pretty sure the company will have something to say about how to handle them. e.g. appropriate SID turn backs or visual terrain clearance.

and someone mentioned earlier that TO software doesn't account for AEO SID requirements. Well it can and does in our case where we can select a specific SID with sometimes limiting gradient requirements. It will then add this limiting AEO case to the list of limiting weights. Lowest one wins as usual.

[Gysbreght]

cosmo cramer:
With 99% likelihood, US1549 departed with derate and assumed temperature thrust reduction. Just to set the record straight, from the NTSB Accident report:
According to the weight and balance manifest provided by US Airways, the airplane departed LGA with a takeoff weight of 151,510 pounds, which was below the maximum limitation takeoff weight of 151,600 pounds.

[Wizofoz]

So? de-rate may still be available at Max Takeoff Weight.

[Gysbreght]

Max. Take-off Weight (structural limit) is 169785 pounds.

[Wizofoz]

Ah! So it was at RTOW! Got it, thanks.

[cosmo kramer]

Gysbreght, I don't get what you are trying to say. At what weight the aircraft departed doesn't say anything about which thrust setting was used.

[Gysbreght]

Ask Wizo, he got it.

[cosmo kramer]

It's not really relevant for the topic. The 151,600 pounds limit could be because of derate. Or maybe they took off with full thrust. I am not familiar with LGA, Airbus or it's performance.

Fact is: 1000s of reduced thrust takeoffs are being made every day where a dual flame out due to bird strike is a (minuscule) potential risk. However, it is not a risk that legally needs to be accounted for.

So again, what are you trying to say? That reduced thrust takeoffs are unsafe because they reduce your margin?

[tasmin]

Maybe a bit off topic, but will post anyway.
B-777 & B-787 AOM and QRH insists that the crew check the Single Engine Go Around capability WITH the GEAR EXTENDED.
QRH Performance section give climb data for GEAR DOWN FLAPS 20 and GEAR DOWN FLAPS 30 Single engine performance.
I cannot find any reference to certification of airplanes go around performance with and engine shut down and the gear left down.
Our AOM for the B-777 dictates the use of flaps 20 for single engine approach as long as performance permits (I interprets that as a stopping performance), hence the G/A configuration is Flaps 5.
To confuse the issue further, the checking of gear down, single engine Go around performance was only required for Auto Lands. Now it is for all approaches.
When raising the question at fleet meetings I am told it is "a B777/B787 thing".