Flap retraction
 

Ok.. I'm bored of the ryanair private jet thread so can anyone put me straight on this..

On a normal all engines operating take off in a business jet we get airborne, romp through V2, go through the speed that the manual says the flaps can go up (V2+20 in mine) and then the most common trigger in companies I have worked for use a height trigger (400 feet for some, 1500 in the one I've just left) to retract the flaps. The challenger is regularly doing 200 ish by that point which is V2+70. I have tried to have the argument many many times that the wing doesnt care how high up it is and we should simply manage the drag the way the manufacturer intended but nobody is having any of it.

What do other people do?

Think the point is nothing to do with the wing. Its about the chance of moving the wrong switch close to the ground and giving yourself a bit of height to get out of trouble if needed.

really? Whats your go-around height on an ILS then?

Company SOP 1000ft (agl), both donks or OEI.

I agree with you though, oei or on a noise departure, you manage the speed, but on a normal day, best to manage the drag.

if you are going so fast close to the ground, why not pull the nose up a bit and gain more altitude?

you may be super light on a reposition flight...do you have option of reduce thrust takeoff?

except for two special airports, we start clean up at 1000' agl, and reduce power at 3000'agl/afe

Deck angle vs gin and tonic in the back!

Derate not allowed by company. Glex climbs like a homesick angel even at max tow.

Why do companies have all engine operating heights for retracting the flaps. In the case of your global for instance, what has height got to do with anything? I realise its an SOP (it is for most companies) but where does it come from? Its got nothing to do with the manufacturers. For the challenger the flaps can be retracted at V2+20. So why does anyone wait for a height?

At my company we call flap speed at V2+25 but do not make any turns until 400' agl.

TomM

It is a double edged sword! Extension of flaps on landing ie in the descent has the effect amongst other things of increasing drag and lift but the aircraft is descending so tapping into potential energy as another source of energy supplied by the engines.
The drag helps control the speed the lift allows the aircraft to fly at VREF for landing.
Takeoff is different we have the lift required to takeoff at a relatively slow speed but with that comes the drag.
Not just from the takeoff flap setting but from the gear and increased AOA!
The gear we get away quickly but we are at max N1 and at slow speed with no potential to tap into potential energy from the airframe should for any reason we need it and limited ability to reduce AOA.
Obviously the main concern in cleaning up in event of an engine failure or loss of power but there is another!
In still air all well and good but in shear conditions that slow speed can become critical.
Hence it is better to concentrate on flying the aircraft in a stable condition until well clear of the ground where you have the ability to tap into potential energy should you need to as well as reducing drag by reducing AOA before going from flap takeoff to zero.

Some say 400agl some 1000agl

Pace

Hello!

In my part of the world, most major airports have noise abatement rules that call for a V2+10kt climb until passing 1500ft AGL before retracting flaps and accellerating. Therefore, many operators have made this (totally arbitrary!) 1500-figure part of their SOPs. Luckily, we are still permitted to do what we want if we precede it with "non standard" ;)

max

About the same as yours, for Cat I...

What I'm trying to suggest is you separate the act of getting airborne with the act of retracting the flaps. Think of it this way, by the sounds of the performance of your jet, you could probably get airborne and by the time you are airborne and have selected gear up, you could probably select flap 0 too.

So, you spend a good few years safely doing this. But you are now at the end of a veeerrrrryyy long week, end of an even longer day and an engine has just failed on you. Unfortunately your motor skills training says that when you select gear up, the flaps go too....

Its about, as I suggested above, error management.

And I'm not suggesting that it would be YOU making these mistakes, just that its possible...

You obviously do not know him then.

Moutrie,
Its all to do with the profile, you raise the flaps at a height to take into account obstacles, NADP 1 NADP 2. If you are flying too fast for the flap speed then manage your speed...
If you retract too soon and then have an engine failure you might not clear the obstacle or on a two engine take off earn yourself a fine for noise...
The wonderful Capt Dyer knows that. He is a sky God...

now you see thats all very interesting info.
APANDY, I think your lot have got it spot on. Get rid of the drag as early as possible - ie, flap up as soon as you're V2+whatever the minimim is, and the no turns before 400' is straight out of document 8168 so that makes sense too.

But why anyone would link a flap retraction to a height is beyond me. I've heard countless arguments and I don't understand any of them! There are no circumstances that I'm aware of where the height makes any difference. A change in flap selection can only be made because of speed - it says so in every aircraft manual written, and it never even mentions height!

Where I think the confusion lies is that there are various certification platforms for an acceleration altitude (ICAO, for instance, use between 400' and 1500') for the acceleration platform in the event of an engine failure but this still is not the criteria for flap retraction - its only about speed!

The arguments about reaching for a lever in the dark on a windy night when you are a bit knackered and finding the wrong one are a bit bizarre to me. Its certainly not a reason to be climbing against the significantly increased drag of having the flaps down! Noise abatement is an interesting one - very few business jet operators I know fly proper noise abatement departures because of the problem of limiting body angle (actually I don't think this is the real reason they don't do it - I think the real reason is they can't be bothered to train properly for it and believe their aircraft are quiet enough thanks very much and they are probably right). But even that doesn't justify leaving the flaps down and increasing the speed against that drag.

What I'm really interested in is where on earth the idea came from that flap retraction is linked to height. In lots of companies its the first call that isnt speed related and I have seen loads of COR's and MOR's related to forgetting to retract the flaps because the 400' call was missed. Big problem here, height is the wrong call to trigger retracting flaps - should be the V2+ call, and its PM moving the eyes to a different instrument at a critical moment that may be at the heart of this. What also bothers me is that some people think that an engine failure means you do something different with the flaps than what you do if the aircraft is operating with all engines (which is at the heart of companies choosing an arbitrary height for both). You DO do the same thing in the event of an engine failure - retract the flaps on the correct speed schedule...

what do you think..?

.. thought of something else pace..

regardless of the conditions, in the event of an engine failure you would fly your plane at V2 flapped to acceleration altitude, take the flaps up at the appropriate speed, and climb away at V2+minimum, then go to an enroute climb speed at an appropriate time. wouldn't you?

So why is there a fear among pilots that selecting flap up at V2+20 will somehow make your aircraft unstable or prone to turbulance? Because its a very common misconception. The amount of lift you need from the wing is significantly reduced in the climb and you will be somewhere around 1.5 Vs so where does the feeling that the aeroplane needs 40 or 50 knots of extra speed from. All we are doing is degrading the 2nd segment climb and therefore wasting fuel and making noise.

just a thought..

Historically this comes from airport design criteria which were matched to aircraft design. Around a round table (many round tables over the years) starting in the 1930ies, representaives of towns and aerodromes and representatives of aircraft manufacturers debated over the obstacle-free zones around aerodromes and the climb performance of aircraft. The aerodrome managers wanted to build as close to town centres as possible, the aircraft manufacturers wanted to use the cheapest engines on the market, and eventually that 400ft compromise evolved that found it's way into both aerodrome layout and part-25-design criteria. If someone wants to do a historical search, I'm pretty sure that 400ft-obstacle which was the origin of all this can still be identified somewhere. Some building around Idlewild or Tempelhof, who knows...

But where on earth this 1500ft-figure came from is a miracle to me. Totally arbitrary, nonsensical, yet part of many training programs and SOPs. Personally, I tend to disregeard it with the exception of my yearly checkride at FSI.

You have to understand that while we scratch our heads at the rationale of some checklists and SOPS, the reality is that you had a bunch of pilots and lawyers in a room cooking this stuff up at certification time....

'Ok, imagine the lowest time, pal/buddy/robot, Chief pilot culled inexperienced moron flying this plane...next to him is a pilot with even less time, less balls..a marshmellow, hoping the pilot has it right, because he's not going to say anything...so when do we have this guy retract the flaps?'

'Well if we have him do it right way...some guy, some where is going to rotate right at stall, then retract the flaps...can't have that...if we make him wait until 1500 feet, chances are some moron will accelerate to 300 kts and rip them off....so tell you what...let's make it 400 feet.....high enough where idiot #1 won't do it to quick.....not so high that idiot #2 will accelerate past Vfe. All those in favor say aye. Now just to cover our butts, let's make the climb out speed less then Vfe, so figure the times to climb for that...ok...so what am I missing? Come on guys...try to imagine a complete retard flying the plane.....what have we missed...yeah yeah...that's right...get the AP on fast...no early turns....good good keep them coming...'

whats next
yes the 400' is part of document 8168 - its in the procedure design criteria bit in section 2 but it still has nothing to do with flap retraction.

Sillypeoples
you're kind of proving my point.. its got nothing to do with height. So when you say newbie might do it at this point or that point the only bit that matters is selecting them at the right speed. In fact, this is exactly where all the confusion comes from!

starting to see a theme here..

So, is there any reason at all for having a height trigger? Has anyone ever seen such a trigger in an aircraft manual?

I'll tell you where I think it all comes from. Flight flipping safety! I'm gonna ask them see if they know..

It's to do with the distance it takes to get from V2 to flap retract speed when an engine fails, each take off or intersection has in theory a different altitude to raise the flaps governed by what you may fly into on the take off flight path.

400 feet is the minimum by regulation, do you really want to fly level at 400 feet trying to speed up to flap retract when it's 40 degrees at Al Bateen and you are heading towards downtown Abu Dhabi at MTOM.

In the mountains you may need to fly V2 to your engines 5 or 10 minute limit before being able to fly level for flap retract. If you don't buy take off perf or calculate it like we are supposed to then 1500 feet has got to be safer than 400 feet for level acceleration?.

hello mr k

I can do a first principles net take off flight path calculation, thats not the issue here. My problem is that all engines operating, most biz jet pilots go rattling through the speed that they can retract the flaps and continue on up to whatever speed they get to by the time they get to 1000' or 1500' or whatever their particular company chooses to to use as a totally arbitrary flap retraction height.

Flap retraction heights don't exist - they are a figment of crappy understanding. There are level acceleration platforms which you can use to get from V2 to whatever speed you need to raise the flaps to the next position but all engines running you don't need them. So you can raise the flaps whenever you like as long as you have achieved the necessary speed.

Its incredible to me that very very few of us do whats in the aircraft manual. A mixture of tribal knowlege and lack of understanding has taught an enormous number of people to do something that doesnt make sense and can't be justified.

The Bank Job is on TV, I can't comment further.

I fly a G550, and 400 ft flap retraction certainly is in the book, thats not all it says, but on the 2 donks profile 400ft is flap retraction height.
What amazes me more, is that companies override what the manufactures set out as a profile.

Any chance you could send me a page reference?
All I can find in the 550 manual is 06-02-00, normal take off with AT which call for gear then flap before the 400 foot call. I think whats in the 550 manual is correct but not what everyone actually does - never flown a 550 though.

Will try to post the page on here.

In the FSI document "G550 PTH", on Preface, page MTP-1, Gulfstream has stated that FSI is in fact their training partner, and that documents produced by FSI, are adopted as standard procedure for ALL Gulfstream aircraft.

On Page 19-13 (Rev 5.2, Oct 2011) it states that at 400 Ft AAL, the command "Flaps Up", Flight Level change" shall be given.

If you can get a hold of this document, it provides excellent standards training for pilots new to Gulfstream aircraft, and anyone flying an older generation aircraft where training documents may be lacking.

I'm not here to start a fight gents, just sharing what I got!

Hope this helps

FR

thanks frank - that confirms my earlier suspicion which is that this comes from Flight Safety. Its definitely not whats in the G550 manual from Gulfstream because I've looked at that and tried to post the page. Its not in the Global manual, the Challenger manual, the Embraer Lineage manual, the Cessna Citationjet manual, or the Embraer Phenom manual.

I'm not trying to start a fight either, I'm simply trying to work out why we don't fly these planes the way the manufacturer suggested during a particularly critical phase of flight and why the belief that we should do otherwise is so deeply ingrained. FSI are responsible for teaching a very large number of pilots and there is a commonly held belief that if it comes from them then its gospel. Maybe it isnt..

You need to hit the aircraft perf charts, for the CL 30 the acceleration altitude is called the transition segment, section 7-19 of the perf data in the operational reference manual.
I use APG for take off calculations and I was given the option when I opened the account to use 400 or 1500 for this segment. If the airport needs higher than 1500 it is published on the APG data sheet.
What normally happens if I can't do 1500 feet then an emergency turn is published by APG.
I fully agree that the aircraft I fly all wizz through flap retract and careful energy managment is required.
The argument for me waiting for 1500 all engines is that should an engine fail I don't need to remember what the profile should be as I do it all the time.
Never say never though as with a low initial level off after take off or with gusty conditions I use 400 feet and if I am freelancing I do what I am told.

And therein lies the answer in my opinion. It's got nothing to do with the aircraft and everything to do with the pilot. I have always believed that we should do exactly the same on every take-off - OEI or normal. When the engine starts spewing metal and the airframe is vibrating your fillings out of your head, you and your crew can just do as you have always done.

As for blasting through minimum flap retract or noise abatement - here's an idea - follow procedures - take off in FLC and reduce power after take off. That's what's in every ops manual for every company that I have flown the CJ for and I can count on one hand the number of pilots I know that do it.

actually, therein lies the problem. You only need to remember a profile to fly at all because of the warped logic coming out of flight safety. The only thing you need to remember (as far as the manufacturers are concerned) is that the flaps on the CJ can come up at V2+10. On the Challenger its V2+20. Phenom its V2+1 and so on. And you always do that whether an engine fails or not. Should you lose an engine before V2+10 (for the CJ and whatever for other aircraft) you will lose a large percentage of your available thrust. You may, therefore, need a level acceleration platform to achieve V2+10 in order to raise the flaps and climb away clean. ICAO introduced two certification platforms - 400 feet and 1500 feet. You will probably remember that the straight CJ happened to be certified at 400 feet but most aircraft now are certified at 1500 feet for a level acceleration platform. The reason was to do with time available at max thrust OEI. In fact, the perversion of leaving the flaps down and climbing at higher speeds against the induced drag causes quite a serious problem - should an engine fail at higher speed when you are still in the take off flap condition, whats your plan? Just consider for a moment where you are - climbing at 160kts against the flap, engine fails at 900 feet (very common for a birdstrike) what do you do?

The reason for taking the flap up at the speed the manufacturer suggests is that is where the L/D curves are closest for the different wing configurations. What you get, therefore, is minimal pitch change, and the most efficient combination of lift and drag for the changing speeds. As soon as you are appreciably over this speed you are simply creating more drag than you need to for the lift you need and there is no case at all for doing this on take off. Its arguable that this is desirable on approach so that you have an element of drag control to help lose speed but on take off all you do is degrade the climb profile and therefore have an associated decrease in safety and increase in noise. Where does it come from?

I think there is quite a serious climb performance gradient issue here which I've done some maths on and there is also an awful lot of confusion caused by poor understanding and incorrect teaching by some of the training organisations (not just flight safety). Pilots talk about different profiles for an all engine operating take off and a loss of thrust condition but in reality they are exactly the same. I just really want to check that I'm not missing something and make sure that no manufacturer issues a manual that tells us to do what everyone is actually doing.

Hi Klaxon, checked and thats all OEI data. Not all engines operating. All that does is add to the fact that you shouldnt be climbing with take off flap at anything significantly above the flap retraction speed otherwise you dont really know where you are along the all engines operating take off path..

Sorry I am getting lost now, I only calculate a single engine NTOFP, maybe you should post in the tec section where all the boffs hang out. Good luck:)

you calculate a single engine net take off path (or more likely a bit of software does it for you) then fly an all engine operating take off and you don't do it the way the manufacturer intended. You hold a take off flap setting, climb against drag, make more noise than necessary, end up in an unknown and unprovable vertical situation with regard to SID gradient, and you use more fuel. And there's no reason for it.

I'll put 100 quid on it. Does that help?

and its not a boffs question. We all do it wrong, we are pilots, we are taught to do it wrong. And I'm pretty sure I can prove it.

Come on, I'll up the bet if you like. But its two way...

On the Hawker, we regularly do flap 0 take-offs. The second segment climb performance is calculated using our computerised programme and/or the aircraft manual and is often better than using flap 15 ( not to mention one less action to undertake at a particularly busy stage of the flight).

Some flight departments like to standardise procedures for all types and this could range from a Citation up to an Airbus. Clearly there are different requirements for different aircraft and a one size fits all policy sometimes appears a little non-sensical. Airmanship dictates how we operate and any variations from SOPs are discussed beforehand and need to justifiable to the men in suits at any subsequent board of inquiry.

AP

AP you are working for the enlightened and thanks for your post. The 125 series aircraft is descended from the Dominie I think which was originally used as an instrument training aircraft by the RAF. When it was used by them it almost always did a flap zero take off because, as you say, its already clean that way and the 2nd segment climb is better. Bizarre then that when its used as a business jet the SOP's get fannied around with and it becomes the norm to take off with flaps set at 15(I think). And then, because the dolt that has written the part B has copied it from someone else, this confusing rubbish about 1500 feet gets thrown into the equation. I advocated taking off in the CJ flap zero at my previous employer and got all sorts of snipes for being experimental.

Nobody want to take the 100 quid bet? I'll up it then to 200. Flight Safety instructors particularly welcome..

Tommoutrie
Yes, the modern Hawker 125 series is descended from the Dominie albeit with more powerful fan engines as opposed to the original constant thrust, variable noise Viper turbojets.

There seems to be confusion between second segment and noise abatement climb profiles and what they are trying to achieve. 1500' agl is the end of the second segment climb and is the point at which you will accelerate, retract flap if used, and accelerate to en-route climb speed, having had an engine fail at V1. The calculation allows for the aircraft in this condition, if flown straight ahead at V2 to 1500', to clear all obstacles to that point. If this is not possible then an emergency turn procedure is devised. At least, that is how our performance programme works, and it will give profiles for both flap 15 and flap 0.

Noise abatement profiles assume both engines operating and are designed to leave as much noise in the vicinity of the airport as possible with as much height gained over distance travelled as possible (vx) prior to cleaning up and reducing power to a level sufficient to give an acceptable rate of climb or height in time (vy) with minimum noise nuisance.The goal of a noise abatement climb is to reduce noise whereas the goal of second segment climb is to clear obstacles.

Now consider a standard departure where both engines function correctly. If the performance calculation shows that you could clear all obstacles to1500'agl if the aircraft is flown correctly with an engine out at V1 with flap 0 or flap 15, then all that is required to stay safe with two engines operating is a sufficient rate of climb to satisfy the requirements of the SID. This is generally less than a 5% gradient which is the same as a standard ILS, or 750'pm at 150kts. The best two engine performance for our aircraft is achieved by initially pitching to 12degrees and retracting flap and reducing power at the calculated flap retract speed, which is usually reached by 400'agl. Leaving flap extended beyond that speed will result in unnecessary drag and a performance penalty. I generally accelerate after flap retraction to 180-200kts for the initial turn on the SID and control rate of climb with power to avoid exceeding 1000'pm in the final 1000' to level-off (our SOP). This profile exceeds the obstacle clearance requirements of a standard SID four-fold on an ISA day at sea level with climb power set!

Clearly, all departures are briefed and profiles adjusted to suit conditions, terrain and airport requirements. I can't think of any scenario, however, when it is advantageous to leave flap at take-off setting past calculated flap retract speed on our aircraft with both engines operating.

Sorry for the ramble, I really haven't been drinking!

AP

That sounds absolutely spot on. I think you are in a tiny minority of operators who are doing it right. Genius! Hey at least that confirms I'm not completely nuts!

The CAE Manual for the G4 states "At VFS (Minimum), select FLCH" so this would have you retract the flaps based on a speed rather than a height.

But of course that's not the way we do it :)

The 400 feet froms from aircraft certification where the limits are between 400-1200 feet, the 1500/3000 feet comes from ICAO noise abatement. They were not developed to meet the same goals, in the same sense as the certified gradient will not protect you for the SID departure gradient requirements.

Mutt

aarrgh!! More evidence from the manufacturer! Why don't we do it like they want us to?

The ICAO level acceleration platforms are 400 to 1500 feet - they are in document 8168. In fact you can choose to certify your plane using any level acceleration platform between and including those two heights but all of that is to do with OEI operation.

NAP1 and NAP2 are noise abatement procedures for close in and slightly further away noise reduction. These are applicable to all engine operating conditions and almost all biz jet operators ignore them deciding that the body angles achieved are too great (there's a body angle max suggestion of 20 degrees). What most operator choose to do is leave the flaps down and accelerate anyway which degrades the take off path and actually causes more noise.

All of this is supporting my argument.

Tell you what... I'm upping the bet to a grand...