Flap retraction
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Sorry, Tom; you're down 2 grand.
First, it's interesting that you keep saying everyone's doing it (in your opinion) wrong because FSI & co have been teaching it for years. The reality is that it's only recently that they've started to teach it after years of pressure to correct their previous errors. They used to teach all sorts of strange things that were not as per manufacturer, and have the court cases to prove it!
Second, a lesson in aerodynamics; V2 is most certainly not the best angle of climb speed. It is the minimum speed for climbing out following an engine failure at V1. On swept wing jets, Vxse is between V2+10 and 20, which is why many manufacturers' advice for an engine failure above V2 is to slow to V2 + 10 or + 20 depending on the type. It is also why when you get into airliner size machines they give you the figures for the option of trading runway length for improved climb by increasing the speeds.
I agree entirely with you that flap retraction is a function of speed, not height. I also agree, I have never seen an AFM or manufacturer's checklist that gives a height, although many say "not below 400ft". The significance of the 1000 or 1500 (or even 400 for those so inclined) is that it is the trigger to start accelerating for flap retraction. The reality is, though, that most bizjets have so much performance that you are normally already past the minimum speed and so can retract the flaps immediately. I have seen crews cockup in the sim when heavy, hot & high due to this not being the case, but just because crews don't understand the SOP (usually due to poor training) doesn't make the SOP wrong.
So why is the SOP as it is? There are two reasons, both of which have already been posted.
The first is NADP's. All EU-OPS operators are required do do them. So before we go any further, anyone retracting flaps at 400' on a European commercial operation is operating illegally. In this context, you are actually better off having some flap down, because the drag and the pitch attitude change of flap helps with the issue of body angle. 15 to 20 degrees is no problem, but more does start to be uncomfortable in the back particularly for pax in rear facing seats.
The second is the engine failure in the climb case. All twin engined jets will do a far better gradient on two engines even at a much higher speed than they will OEI. For example, at 200 knots 2000fpm is a 10% gradient. That is off the scale for most aircraft OEI. So in the event of an engine failure in the climb you are already above the NTOFP. During the period of reducing speed to V2+10 you will be climbing better than at the steady V2 had you had an engine failure, and when steady at V2+10 you will still be climbing better, see above. So you have guaranteed your obstacle clearance.
However, if at some point before the engine failed you have retracted the flaps, while you start off in the same position you rapidly move into no man's land. You mention the Challenger; there is no second segment speed clean because flaps up is not an approved takeoff configuration. So what speed should you fly? And what is the performance at that speed? If you fly at Vfto/Venr or whatever the manufacturer calls it, you may or may not have to accelerate to reach that, and the gradient may or may not be better than V2 with flaps. Most of the time it is, but not always. And the passengers are not paying for "most of the time" or "probably" - they are paying for definite answers.
So to summarise, leaving flap retraction to 1500ft or similar has advantages in being the approved noise abatement procedure and guaranteeing obstacle clearance in case of an engine failure, with the bonus of the commonality of procedures between normal and OEI ops also mentioned. So why do it any other way?
Interestingly, if you read D.P. Davies, the airlines were having this discussion 30 years ago. It's nice to know we're at the cutting edge of the industry!
So, Tom, you can send the cheque to me made out to the Campaign Against Sobriety and Hunger (C.A.S.H. will do!)
First, it's interesting that you keep saying everyone's doing it (in your opinion) wrong because FSI & co have been teaching it for years. The reality is that it's only recently that they've started to teach it after years of pressure to correct their previous errors. They used to teach all sorts of strange things that were not as per manufacturer, and have the court cases to prove it!
Second, a lesson in aerodynamics; V2 is most certainly not the best angle of climb speed. It is the minimum speed for climbing out following an engine failure at V1. On swept wing jets, Vxse is between V2+10 and 20, which is why many manufacturers' advice for an engine failure above V2 is to slow to V2 + 10 or + 20 depending on the type. It is also why when you get into airliner size machines they give you the figures for the option of trading runway length for improved climb by increasing the speeds.
I agree entirely with you that flap retraction is a function of speed, not height. I also agree, I have never seen an AFM or manufacturer's checklist that gives a height, although many say "not below 400ft". The significance of the 1000 or 1500 (or even 400 for those so inclined) is that it is the trigger to start accelerating for flap retraction. The reality is, though, that most bizjets have so much performance that you are normally already past the minimum speed and so can retract the flaps immediately. I have seen crews cockup in the sim when heavy, hot & high due to this not being the case, but just because crews don't understand the SOP (usually due to poor training) doesn't make the SOP wrong.
So why is the SOP as it is? There are two reasons, both of which have already been posted.
The first is NADP's. All EU-OPS operators are required do do them. So before we go any further, anyone retracting flaps at 400' on a European commercial operation is operating illegally. In this context, you are actually better off having some flap down, because the drag and the pitch attitude change of flap helps with the issue of body angle. 15 to 20 degrees is no problem, but more does start to be uncomfortable in the back particularly for pax in rear facing seats.
The second is the engine failure in the climb case. All twin engined jets will do a far better gradient on two engines even at a much higher speed than they will OEI. For example, at 200 knots 2000fpm is a 10% gradient. That is off the scale for most aircraft OEI. So in the event of an engine failure in the climb you are already above the NTOFP. During the period of reducing speed to V2+10 you will be climbing better than at the steady V2 had you had an engine failure, and when steady at V2+10 you will still be climbing better, see above. So you have guaranteed your obstacle clearance.
However, if at some point before the engine failed you have retracted the flaps, while you start off in the same position you rapidly move into no man's land. You mention the Challenger; there is no second segment speed clean because flaps up is not an approved takeoff configuration. So what speed should you fly? And what is the performance at that speed? If you fly at Vfto/Venr or whatever the manufacturer calls it, you may or may not have to accelerate to reach that, and the gradient may or may not be better than V2 with flaps. Most of the time it is, but not always. And the passengers are not paying for "most of the time" or "probably" - they are paying for definite answers.
So to summarise, leaving flap retraction to 1500ft or similar has advantages in being the approved noise abatement procedure and guaranteeing obstacle clearance in case of an engine failure, with the bonus of the commonality of procedures between normal and OEI ops also mentioned. So why do it any other way?
Interestingly, if you read D.P. Davies, the airlines were having this discussion 30 years ago. It's nice to know we're at the cutting edge of the industry!
So, Tom, you can send the cheque to me made out to the Campaign Against Sobriety and Hunger (C.A.S.H. will do!)
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out of interest, does anyone actually agree with me?
I spent more than an hour flying my amphibian over the water yesterday, and obeying the 400 foot "rule" for flap retraction, I would not have retracted them the whole hour, as I did not get higher than 200 above the water....
The first is NADP's. All EU-OPS operators are required do do them. So before we go any further, anyone retracting flaps at 400' on a European commercial operation is operating illegally.
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Sorry, the curse of acronyms! NADP's = noise abatement departure procedures, so not relevant to balked landings.
And this whole discussion is about transport style jet ops - not real flying! I don't think I'd stay employed for very long if I did a whole trip below 400 feet, but it might be worth it....
And this whole discussion is about transport style jet ops - not real flying! I don't think I'd stay employed for very long if I did a whole trip below 400 feet, but it might be worth it....
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Which brings us to another quandry.
On the aircraft I currently fly (G-IV-SP)
The manuals all state flaps up not below 400ft. Although I must admit that I found an earlier (1999) CAE training checklist stating : on positive rate of climb - gear up , flaps up.
However, if we work it backwards slightly, on an all engines operating go-around, there is nothing about a 400ft min for cleaning up, it just clearly states flaps up at V2+20. Which brings us back to Tom's question of why the 400ft 'limit' is there in the first place, if we are expected to clean up the flaps at V2+20 on a go-around. Why then not on a normal departure?
In the case of the G-IV its actually much of a muchness, in that on a normal all engines departure, selecting gear up on positive rate of climb and waiting for the lights to go out, leaves you at just about 300-400ft, on speed, ready to retract the flap. Thus we are quite happy to stick to the prescribed 400ft flap up, FLCH call as prescribed during training, as its near as dammit to lifting the flap as soon as the gear is confirmed stowed away.
On the aircraft I currently fly (G-IV-SP)
The manuals all state flaps up not below 400ft. Although I must admit that I found an earlier (1999) CAE training checklist stating : on positive rate of climb - gear up , flaps up.
However, if we work it backwards slightly, on an all engines operating go-around, there is nothing about a 400ft min for cleaning up, it just clearly states flaps up at V2+20. Which brings us back to Tom's question of why the 400ft 'limit' is there in the first place, if we are expected to clean up the flaps at V2+20 on a go-around. Why then not on a normal departure?
In the case of the G-IV its actually much of a muchness, in that on a normal all engines departure, selecting gear up on positive rate of climb and waiting for the lights to go out, leaves you at just about 300-400ft, on speed, ready to retract the flap. Thus we are quite happy to stick to the prescribed 400ft flap up, FLCH call as prescribed during training, as its near as dammit to lifting the flap as soon as the gear is confirmed stowed away.
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ok Emptycruise and BizJetJock you seem pretty sure of your ground.
Would you like to actually take the bet?
I'm perfectly happy to leave it at a grand but if you're not so sure we can make it a pint. Either way, witnessed by all and sundry.
Would you like to actually take the bet?
I'm perfectly happy to leave it at a grand but if you're not so sure we can make it a pint. Either way, witnessed by all and sundry.
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By the way, my point, once again, is that we should do it exactly as per the AFM. Nothing I've suggested at any point in this thread suggests otherwise and furthermore, I'm pretty sure that most business jet operators don't fly the take off as per the AFM. I kind of think we should.
Anyway.. bet on? you can name the stake.
Anyway.. bet on? you can name the stake.
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Haven't got time to post the docs, but I've just checked the AFM's of the CJ2+ and the CL601 (since you mentioned types). Both of them, in the "normal procedures, after takeoff", just say "Landing gear - up; flaps - 0". So as far as lawyers are concerned, either way of doing it is complying with the AFM.
I'll call that a beer.....
I'll call that a beer.....
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400' Origin
On the first generation jets with water injection 400' was used to allow for a level off and acceleration to clean speed.
They wanted to ensure that they would attain the required speed before the water was consumed.
We still use it today for normal ops in our G450/550, but we have so much power it's not required anymore. In the event of an engine failure we climb to 1500' or a safe obstacle clearing altitude prior to acceleration and flap retraction. (With two donks running and flaps 20 we would overspeed the flaps unless we had a 40 degree deck angle).
They wanted to ensure that they would attain the required speed before the water was consumed.
We still use it today for normal ops in our G450/550, but we have so much power it's not required anymore. In the event of an engine failure we climb to 1500' or a safe obstacle clearing altitude prior to acceleration and flap retraction. (With two donks running and flaps 20 we would overspeed the flaps unless we had a 40 degree deck angle).
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Hello Emptycruise
Do you mind if I include a couple of bits of what you posted so that I can reply to them?
1) Operators flying all-engines operating with a fixed pitch and getting alarmingly close to VFE before retracting flaps on a normal departure.
Yes this is what I'm particularly concerned about and has been the thrust of the post from the start.
2) The aerodynamic efficacy of the aircraft operating at V2-V2+10 with TO flaps vs V2+whatever clean
I am certainly not advocating climbing clean at V2+whatever. I'm suggesting that if we are not doing a noise abatement departure we take the flaps up once we are above the AFM flap up speed and continue to accelerate to at least Venr and then onto a sensible initial climb speed for the aircraft.
Noise abatement causes specific problems for high powered business jets so we could debate these as well if you like.
Issue 2 - still not buying it. From an aerodynamic POV you might very well be right, but with no way of making the manufacturer accept your evidence.
I am suggesting we climb the aircraft exactly as the manufacturer suggests.
1) V2 and Flaps TO (or back to V2+10 if failure occurred after this speed)
This doesnt make any sense. All engines operating, no manufacturer suggests that for a normal departure we climb at V2. In the case of an aircraft where the flaps come up at V2+10, the manufacturer expects us to raise the flaps at V2+10 (which hardly anyone does). If we are at a speed over V2+10 and clean we would hold that speed. If you were at a speed appreciably above that you would increase the pitch to reduce speed to V2+10 (although in practical terms it may make more sense to simply reduce the speed to Venr). This IS what the manufacturers intend us to do. The aircraft will climb more efficiently clean than in the flapped condition. The whole point is that if the failure occurs before the flaps are raised that we do not have enough excess power to accelerate and climb (well thats where the theory comes from) and we have a demonstrable net take off flight path if we delay the acceleration to a known platform. That is not always 1500 feet. There are a number of other limitations which may mean the available acceleration platform is lower - one of which is the time you have available at max thrust on one engine.
Now, apart from waving Ockhams Razor at you - suggesting that the simplest explaination for OEMs chosing Vfto as your clean climb-speed because this is the most effective gradient speed, thus having the best performing and thus best selling aircraft they can - I simply must disagree with the idea of flying the aircraft in a radically different configuration than the OEM tells you to, especially just after losing one engine. This apart from the arguments stated in my previous post...
Nowhere am I suggesting flying the aircraft in a manner which is not consistent with the AFM. I am suggesting that the most common way that we are told to operate these aircraft is not in accordance with the AFM. I am directly suggesting that the majority of SOP's do not understand what the AFM actually says. I am suggesting that all engines operating it is ridiculous to use a height to trigger whether or not to raise the flap. It doesnt exist in the regulations, it doesnt exist in the FAR's, it doesnt exist in the JAR's and its been incorrectly interpreted from the situation where a powerplant fails.
If the G650 AFM says gear+flaps up at the same time
I'm absolutely certain that the 650 will have a flap up speed, V2+whatever, and it tells the crew to take the flap up at that point. So does every other aircraft, yours included (what is it by the way and I'll look it up).
It may be more efficient going clean @ V2+whatever - but why would I do it? I check for each and every departure that I can clear all obstacles using the AFM speeds and configuration, so I would gain nothing by going down the path you suggest.
For all the reasons stated previously, ie noise, fuel burn etc. Also, if you are saying you fly every single departure to 1500 feet without the speed going over the flap up speed then fair enough but if you exceed that speed (in all honesty it has to be by a bit) then you are creating extra drag and degrading your all engines operating flight path. Thats simply bad airmanship because if you do lose an engine you have to pitch for longer to get back to V2 to V2+10 (and just that pitching causes a fair amount of drag so the longer you pitch, the more drag you make) and when you get there you don't climb as well as you would if you were a bit over V2+10 and clean. Because that is where the manufacturer intended you to be.
I cannot lift more mass out of a given runway
True but because you haven't burned it you do carry a little bit more fuel to altitude and there is absolutely no penalty. You burn that fuel churning up the air with your flaps!
but by using non-standard procedures I leave myself wide open to attack from lawyers, to career-ending rumours about my person and ridicule from my peers.
In fact, this is my point. Although its very unlikely, I honestly believe that the slightly confused way we are taught and the lack of understanding it leaves the majority of pilots with means that it is the vast majority of us that are operating outside what the manufacturer has intended. Perhaps you included!
In other words - you may have an aerodynamically point
you might mean an aerodynamically correct point and I do
but from an operational point it's a non-starter.
really? why?
Once again, please show me the business jet AFM which says what we are all commonly doing is correct. I'm actually not saying it doesnt exist, but I am saying that for all the types I've ever come across it is clear we are not doing it correctly. What type do you fly EmptyCruise?
Do you mind if I include a couple of bits of what you posted so that I can reply to them?
1) Operators flying all-engines operating with a fixed pitch and getting alarmingly close to VFE before retracting flaps on a normal departure.
Yes this is what I'm particularly concerned about and has been the thrust of the post from the start.
2) The aerodynamic efficacy of the aircraft operating at V2-V2+10 with TO flaps vs V2+whatever clean
I am certainly not advocating climbing clean at V2+whatever. I'm suggesting that if we are not doing a noise abatement departure we take the flaps up once we are above the AFM flap up speed and continue to accelerate to at least Venr and then onto a sensible initial climb speed for the aircraft.
Noise abatement causes specific problems for high powered business jets so we could debate these as well if you like.
Issue 2 - still not buying it. From an aerodynamic POV you might very well be right, but with no way of making the manufacturer accept your evidence.
I am suggesting we climb the aircraft exactly as the manufacturer suggests.
1) V2 and Flaps TO (or back to V2+10 if failure occurred after this speed)
This doesnt make any sense. All engines operating, no manufacturer suggests that for a normal departure we climb at V2. In the case of an aircraft where the flaps come up at V2+10, the manufacturer expects us to raise the flaps at V2+10 (which hardly anyone does). If we are at a speed over V2+10 and clean we would hold that speed. If you were at a speed appreciably above that you would increase the pitch to reduce speed to V2+10 (although in practical terms it may make more sense to simply reduce the speed to Venr). This IS what the manufacturers intend us to do. The aircraft will climb more efficiently clean than in the flapped condition. The whole point is that if the failure occurs before the flaps are raised that we do not have enough excess power to accelerate and climb (well thats where the theory comes from) and we have a demonstrable net take off flight path if we delay the acceleration to a known platform. That is not always 1500 feet. There are a number of other limitations which may mean the available acceleration platform is lower - one of which is the time you have available at max thrust on one engine.
Now, apart from waving Ockhams Razor at you - suggesting that the simplest explaination for OEMs chosing Vfto as your clean climb-speed because this is the most effective gradient speed, thus having the best performing and thus best selling aircraft they can - I simply must disagree with the idea of flying the aircraft in a radically different configuration than the OEM tells you to, especially just after losing one engine. This apart from the arguments stated in my previous post...
Nowhere am I suggesting flying the aircraft in a manner which is not consistent with the AFM. I am suggesting that the most common way that we are told to operate these aircraft is not in accordance with the AFM. I am directly suggesting that the majority of SOP's do not understand what the AFM actually says. I am suggesting that all engines operating it is ridiculous to use a height to trigger whether or not to raise the flap. It doesnt exist in the regulations, it doesnt exist in the FAR's, it doesnt exist in the JAR's and its been incorrectly interpreted from the situation where a powerplant fails.
If the G650 AFM says gear+flaps up at the same time
I'm absolutely certain that the 650 will have a flap up speed, V2+whatever, and it tells the crew to take the flap up at that point. So does every other aircraft, yours included (what is it by the way and I'll look it up).
It may be more efficient going clean @ V2+whatever - but why would I do it? I check for each and every departure that I can clear all obstacles using the AFM speeds and configuration, so I would gain nothing by going down the path you suggest.
For all the reasons stated previously, ie noise, fuel burn etc. Also, if you are saying you fly every single departure to 1500 feet without the speed going over the flap up speed then fair enough but if you exceed that speed (in all honesty it has to be by a bit) then you are creating extra drag and degrading your all engines operating flight path. Thats simply bad airmanship because if you do lose an engine you have to pitch for longer to get back to V2 to V2+10 (and just that pitching causes a fair amount of drag so the longer you pitch, the more drag you make) and when you get there you don't climb as well as you would if you were a bit over V2+10 and clean. Because that is where the manufacturer intended you to be.
I cannot lift more mass out of a given runway
True but because you haven't burned it you do carry a little bit more fuel to altitude and there is absolutely no penalty. You burn that fuel churning up the air with your flaps!
but by using non-standard procedures I leave myself wide open to attack from lawyers, to career-ending rumours about my person and ridicule from my peers.
In fact, this is my point. Although its very unlikely, I honestly believe that the slightly confused way we are taught and the lack of understanding it leaves the majority of pilots with means that it is the vast majority of us that are operating outside what the manufacturer has intended. Perhaps you included!
In other words - you may have an aerodynamically point
you might mean an aerodynamically correct point and I do
but from an operational point it's a non-starter.
really? why?
Once again, please show me the business jet AFM which says what we are all commonly doing is correct. I'm actually not saying it doesnt exist, but I am saying that for all the types I've ever come across it is clear we are not doing it correctly. What type do you fly EmptyCruise?
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one thing that I'm going back to my university books for is the relationship between V2 and Vx. V2 is a computed speed which cannot be less than Vs. Vx all engines operating can be well below Vs depending on available thrust, take off mass, loading, airfoil section, all sorts of things. Vx OEI (Vxse would discount all the three and four engined pilots out there and I'm all about inclusion) is always higher than Vx all engines (provided all the other considerations remain the same) but from memory is usually very close to V2. Vy is usually a bit above V2.
I'm currently buried in Roksam Airplane Aerodynamics and Performance to try to work out the answer. Taint easy.. In fact, that one I will search the teccies corner for..
I'm currently buried in Roksam Airplane Aerodynamics and Performance to try to work out the answer. Taint easy.. In fact, that one I will search the teccies corner for..
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Really good discussion.
i wonder if the 400ft is more about getting out of ground effect, getting some distance between you and the ground in the event of windshear etc and establishing a stabilised flight path before thinking about touching some buttons. So possibly more about the possibility of human error close to the ground than anything else.
i wonder if the 400ft is more about getting out of ground effect, getting some distance between you and the ground in the event of windshear etc and establishing a stabilised flight path before thinking about touching some buttons. So possibly more about the possibility of human error close to the ground than anything else.
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Tom,
First off let me just say that I tend to agree with your argument and would consider myself to be on your side. However having just finished school on the G650 I can assure you that in the AFM and the Operating Manual there is no speed mentioned in relation to raising the flaps. For both flaps 10 and flaps 20 take-off the climb checklist calls for gear up and next flaps up.
For interest sake it is FSI that has the 400' call included prior to raising the flaps.
First off let me just say that I tend to agree with your argument and would consider myself to be on your side. However having just finished school on the G650 I can assure you that in the AFM and the Operating Manual there is no speed mentioned in relation to raising the flaps. For both flaps 10 and flaps 20 take-off the climb checklist calls for gear up and next flaps up.
For interest sake it is FSI that has the 400' call included prior to raising the flaps.
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A Pandy, a similar statement is in the older Gulfstream Manuals, where Flap retraction is based on speed and not altitude. However have Gulfstream made any software available to you, to prove that you can clear obstacles in the takeoff flight path with all engines operating?
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Well I think he's right - and I know him so that really is saying something.
Some people here (no names, no insult intended and no personal attacks) just are not reading what he's saying (he never once advocated flying outside the AFM instructions) or just cannot consider that their SOPs may be based on folklore.
He is being as clear as he can be - it makes sense to me. It surely is self-evident that flap retraction is unrelated to height?
As for those who feel more 'comfortable' not touching levers below 400ft - what about the gear? Do you leave that down? Climb-power? Mode Select? Does it all hang out until AA or is it just the flap lever you won't lay hands upon?
(Just joking - no fight wanted - this really has been an unfeasibly good-natured 6 page thread)
Some people here (no names, no insult intended and no personal attacks) just are not reading what he's saying (he never once advocated flying outside the AFM instructions) or just cannot consider that their SOPs may be based on folklore.
He is being as clear as he can be - it makes sense to me. It surely is self-evident that flap retraction is unrelated to height?
As for those who feel more 'comfortable' not touching levers below 400ft - what about the gear? Do you leave that down? Climb-power? Mode Select? Does it all hang out until AA or is it just the flap lever you won't lay hands upon?
(Just joking - no fight wanted - this really has been an unfeasibly good-natured 6 page thread)
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It surely is self-evident that flap retraction is unrelated to height?
But again, please don't look at the flap retraction in isolation. Firstly, why do you want to rush? Secondly, how can you prove that you will clear the takeoff obstacles? There is nothing in the AFM for all engine obstacle clearance as its not required by regulation?
As an airline, we increased the 400 feet to 800 feet and took the associated weight loss, we use 1000 feet for all engine, that philosophy was carried over to the corporate fleet.
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Originally Posted by Mutt
Firstly, why do you want to rush?
Originally Posted by Mutt
There is nothing in the AFM for all engine obstacle clearance as its not required by regulation?
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Hello Mutt
Same as above, hope you dont mind if I cut and paste your original post.
Firstly, why do you want to rush?
I'm not suggesting you rush. I'm suggesting that, in the same way as we note "positive rate" and call for gear up that we say "V2+20" and call for flaps up. (its V2+20 on my plane). When the PM calls "Positive Rate" you don't wait to climb to 400 (or 800) feet because you might possibly move the wrong lever, you get rid of the drag. Why is the same not true with the flap?
Secondly, how can you prove that you will clear the takeoff obstacles?
I have complied fully with the AFM therefore I will clear the close in obstacles and everything in the net take off flight path. I was all engines operating to V2+20 and continued the climb at a gradient in excess of the PDG. At any point I could have lost an engine and remained above the PDG. I dont think the calculation is as easy if you go busting through the flap up speed and leave them down thus degrading the climb with drag because thats not what the AFM says.
As an airline, we increased the 400 feet to 800 feet and took the associated weight loss, we use 1000 feet for all engine, that philosophy was carried over to the corporate fleet.
On what basis did you do that? Is it in the AFM? Seems amazing to me that operators make these sweeping decisions and there's no basis in aeronautical logic. Which aircraft types is this for? I don't understand how these policies get written and over-ride the manufacturers manuals for the planes.
I'm going to try to arrange a meeting with Flight Safety at some point this week to chat about this. I've also been promised a call back by one of Bombardier's guys tomorrow. How about I report the result of those conversations on here when they happen?
Same as above, hope you dont mind if I cut and paste your original post.
Firstly, why do you want to rush?
I'm not suggesting you rush. I'm suggesting that, in the same way as we note "positive rate" and call for gear up that we say "V2+20" and call for flaps up. (its V2+20 on my plane). When the PM calls "Positive Rate" you don't wait to climb to 400 (or 800) feet because you might possibly move the wrong lever, you get rid of the drag. Why is the same not true with the flap?
Secondly, how can you prove that you will clear the takeoff obstacles?
I have complied fully with the AFM therefore I will clear the close in obstacles and everything in the net take off flight path. I was all engines operating to V2+20 and continued the climb at a gradient in excess of the PDG. At any point I could have lost an engine and remained above the PDG. I dont think the calculation is as easy if you go busting through the flap up speed and leave them down thus degrading the climb with drag because thats not what the AFM says.
As an airline, we increased the 400 feet to 800 feet and took the associated weight loss, we use 1000 feet for all engine, that philosophy was carried over to the corporate fleet.
On what basis did you do that? Is it in the AFM? Seems amazing to me that operators make these sweeping decisions and there's no basis in aeronautical logic. Which aircraft types is this for? I don't understand how these policies get written and over-ride the manufacturers manuals for the planes.
I'm going to try to arrange a meeting with Flight Safety at some point this week to chat about this. I've also been promised a call back by one of Bombardier's guys tomorrow. How about I report the result of those conversations on here when they happen?
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Join Date: Jan 2002
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sorry mutt - read my post and it reads like I'm calling your department idiots and I'm really not. I think this kind of potentially flawed logic is very widespread indeed and I don't know why its happened. Lets see what the boffins at Bombardier and Flight Safety come up with - if a lowly pilot bod like me can get through to them..