Pitch. It changes when I make a mode selection.

If you choose to take the flaps up at 400 feet at V2+20 the aircraft is still compliant. It has to comply with the climb gradient and I think its clear from all the posts on here that everyone agrees that if you take the flap up at 400 feet it will still comply with the climb. Thats what most people think the normal take off is - flaps up at 400 feet with a speed check of V2+20 (for my plane, different on others). Everyone seems happy that its compliant from 400 feet - well lets check that.. is everyone happy? Or is anyone of the opinion that once clean, if you have an engine failure you should reduce speed to V2 and reselect the take off flap? I've had that one sent privately too..

The flaps neither know nor care how high the aircraft is. If the gradient clean from 400 feet is good enough it will be good enough from wherever you actually select the flaps up because it will be the same gradient because the speed is correct.

I'm really open to the flaws in this but its exactly whats in the Bombardier manual and various Cessna manuals and the Embraer manual. The problem is that they don't explicitly deal with the engine failure after flap retraction in the climb case. They only deal in detail with the engine failure at V1 case.

I've got no issue with using 400 feet as a platform below which there should not be a flap retraction but I think its important that pilots retract the flap for the correct reason. I also think that its important that people understand whats happening. Close inspection of the 737 manual discusses reduced acceleration altitudes in the case of hot and high performance precisely because the gradient and climbs achieved once clean are better than the flapped gradients and climbs.

I'll be completely honest here. I've received a couple of fairly unpleasant emails regarding my professionalism and its not the sort of thing I enjoy reading so its time for me to call a halt to this. I'm sorry I brought it up!

No need to be sorry, the guy(s) sending you mails like that should be ashamed.

I personally like someone who still thinks about things 'later' in its career way better than the guys who don´t. As long as one can discuss without resorting to personal abuse its all fine to me.
The thread served at least to make me rethink procedures etc., although I think I operated in line with the manual/training.... Thanks for that, Tom! :D

Not quite true, Tom. The JAR's and FAR's also state that the minimum flap retraction height is 400'. My present types (JAR/FAR 25 type) AFM also states this height, although its a rocket and speed is usually way above V2+10 way before this height.

This is another thread on the subject here:

http://www.pprune.org/tech-log/31985...-altitude.html

hello 500 above

As discussed before, the conditions for both the FAR25 and JAR 25 are for the failure of the critical operating engine at V1. 400 feet is a certification limit under these conditions. Earlier in this thread I've explained why I believe this does not prohibit the retraction of the flap in the case where all engines are operating. That is also why the AFM's do not refer to 400 feet in relation to flap retraction on an all engines operating take off.

I'm definitely not saying that no AFM exists which has this condition written in. I am, however, saying that the case of an engine failure after the flap retraction speed or even further up the climb, is not explicitly defined. Perhaps you could read a couple of the earlier posts regarding this to see if they make sense - if they don't, then post. You may be absolutely correct and I may have completely missed something.

cheers

Tom, you're missing a couple of fairly fundamental points.

First, the AFM's on all these aircraft are pretty vague on operating detail, precisely because they expect operators to write procedures based on local conditions and requirements. So it doesn't prohibit retracting the flaps as soon as you can, and it also doesn't prohibit leaving them extended.

Second, other rules apply. I know you fly for an EU-OPS operator, so every takeoff where you don't fly a NADP is illegal. Also every takeoff where you don't follow your Part B is illegal. So if your Part B doesn't contain a NADP (it doesn't have to be exactly one of the ICAO profiles) that makes your entire fleet non-compliant. The fact that CAA audits haven't picked this up is not a defence in court, it is the operator's responsibility. And if you as the captain choose to operate illegally, good luck.

With those points in mind, then the profile used by several Challenger operators is quite sensible. The ICAO brief is V2+20 or as limited by body angle to 800 feet then reduce power and either start accelerating to clean up or leave flaps down to 3000 then accelerate. V2+20 for a Challenger varies between 150 and 180 depending on the conditions, but the body angle particularly at light weights gets excessive, so by saying 190 it keeps the pitch below 20 degrees and the speed below Vlo. Note that you are flying a target speed; if you just hold a pitch you can easily at light weights exceed the gear limit speed before the doors have closed. Leaving the flaps down helps!!It gives you a lower pitch angle for any given speed and the drag also helps keep the performance reasonable. They then use 1500 feet as an acceleration height as being both a reasonable compromise between the 800' and 3000'options while giving a common procedure with the engine failure case. In the event of an engine failure below 1500' all you have to do is control the yaw (easier with the higher speed) and let the speed drift back to V2+10 safe in the knowledge that you are above the obstacle clearance profile. And also, again, note that 1500' is the acceleration height; in practice on a normal departure you are already well above the minimumflap retraction speed in the AFM, so can do so immediately.

Now, against that, can you actually tell me what is the advantage of retracting the flaps asap after takeoff?

We call it AA, min height for change from takeoff thrust to climb thrust. Doesn't matter what the term is, its the meaning...

Another 400' reference that I have found is contained in the 737 QRH. It contains the normal takeoff profile which shows earliest points for things to happen. 400' is the earliest point you start anything...

Takeoff profiles - From what I've read, you maintain max thrust till after flap retraction, we reduce thrust before. To accelerate to 250 kt (initial climb speed) takes a few miles (at 1000fpm ish). So say I were to start that after take off once the gear is up, we would be flying very low for a few miles and trust me, if the company didn't get me the journalists would (for low flying...)(rightly...)

Lastly, You've said that clean at V2+20 you get a better climb rate than with flaps out at V2 and you have the graph to prove it. I accept that, but a quick question is, do you have a climb graph for takeoff flap and V2+20? Improved climb is a well researched area...

Thats a good post biz, thanks.

Ok

First, the AFM's on all these aircraft are pretty vague on operating detail, precisely because they expect operators to write procedures based on local conditions and requirements. So it doesn't prohibit retracting the flaps as soon as you can, and it also doesn't prohibit leaving them extended.

That is absolutely correct.

then the profile used by several Challenger operators is quite sensible. The ICAO brief is V2+20 or as limited by body angle to 800 feet then reduce power and either start accelerating to clean up or leave flaps down to 3000 then accelerate. V2+20 for a Challenger varies between 150 and 180 depending on the conditions, but the body angle particularly at light weights gets excessive, so by saying 190 it keeps the pitch below 20 degrees and the speed below Vlo.

I agree with most of that but I don't agree that exceeding V2+20 flapped is of any benefit at all. If you are light and your V2 is 130, V2+20 is 150. If you fly a correct noise abatement profile you will reach 2000 feet at a point which is 2/3rds of a mile closer to the airport than you would if you did it at 190 ie at 2.5 miles rather than at almost 3.2 miles. The whole point of noise abatement is to reduce the noise footprint for close neighbours of the airfield whether it be NADP1 or 2 so I'm not sure the profile you've described fulfils the requirement. For some time I've tried to find a way to negotiate with the authorities from the standpoint of my former career as an acoustic engineer and argue that with the power to weight issues that small business jets have that an earlier power reduction to contain climb rate and limit body angle is far more sensible than trying to contain it by excess drag. It makes no sense to respect one part of the guidelines and ignore another and reducing power would make much more sense. This is why I suggested another thread for discussing noise abatement.


Note that you are flying a target speed; if you just hold a pitch you can easily at light weights exceed the gear limit speed before the doors have closed. Leaving the flaps down helps!!It gives you a lower pitch angle for any given speed and the drag also helps keep the performance reasonable. They then use 1500 feet as an acceleration height as being both a reasonable compromise between the 800' and 3000'options while giving a common procedure with the engine failure case.

Again, controlling the speed with extra drag on take off is contrary thinking in my opinion. Surely a power reduction is more sensible. Explicit in the regulations is that departure from published noise procedures is permissible for reasons of good airmanship and exceeding a limiting factor on the aircraft is surely one of those. But I think a group approach with regard to discussing this with the authorities would be a good idea.

In the event of an engine failure below 1500' all you have to do is control the yaw (easier with the higher speed) and let the speed drift back to V2+10 safe in the knowledge that you are above the obstacle clearance profile. And also, again, note that 1500' is the acceleration height; in practice on a normal departure you are already well above the minimumflap retraction speed in the AFM, so can do so immediately.


Slightly confused as to what you're saying here - I would argue that if you were climbing in excess of V2+20 and had raised the flap there would be no need to fly an acceleration segment (as previously discussed) and the fact that you have had to slow down from 190 (in this case thats V2+60) to V2+10 and then pitch for level acceleration to accelerate back up to V2+20 to raise the flap will degrade the net climb gradient far more than simply reducing speed to V2+20 and climbing at that. Actually there is still a level acceleration segment for both these because there's a further acceleration to 190 for the enroute climb but I think thats obvious to all.

Now, against that, can you actually tell me what is the advantage of retracting the flaps asap after takeoff?


Ok. Firstly I'm not sure that the profile you described is compliant (exceeding V2+20 by such a large amount) and if you are going to fly a non compliant noise departure you may as well make it as quiet as possible. I would suggest that cleaning up and climbing with reduced thrust (ie not climbing against drag) would be a more efficient way to do this but from a compliance point of view the best thing to do is fly the NADP as laid out. As stated before, I don't think its an easy profile for us to fly and we should negotiate with the authorities to get a more sensible profile for business jets but until that time I think we have to do what we have to do.

Also, this isn't a discussion about Challengers. Soverigns, XLS's, even aircraft like the Phenom 300 and the CJ3 really struggle to implement these rules correctly - most just don't bother. So why don't we try to solve the problem?

Also, climbing against drag wastes fuel. Not much fuel I'll give you that but I don't understand the philosophy of wasting any at all.

Humour me specifics, what regulations impose a restriction on flap retraction. Company procedures don't count as this discussion is abut the 'why'.

Roger, FAR 25.111, I'm sure that CASA have a similar regulation. This however deals with an engine failure at VEF. Now if you can get your aircraft manufacturer to guarantee that you will clear all obstacles in the takeoff flight path if you immediately retract the flaps at V2+X, then this conversation is over. However, none of us have certified data stating this, and therein lies the problem, we aren't looking at this from a purely aerodynamic point of view, we are looking at being able to prove regulation compliance with our operating authorities, or in the event we ever end up in a court room.

Tom, the fact that you have never heard of extended second segment shows me that you have never dealt with the concept of increasing the acceleration height to clear obstacles, we can have the second segment climb continue for almost 10 minutes, with this in mind, its much easier to only have a procedure based on an altitude rather than a speed.

Unfortunately manufacturers usually only certify the data that is required for the AFM, primarily due to time and cost constraints, this leads to things being treated in isolation, they will look at the requirements for FAR 25.111, they wont certify this procedure for all engines. Your aerodynamic argument is good for small aircraft, it doesn't work for larger aircraft, as someone else has posted, it takes them too long to accelerate to the retraction speed.

But the fact remains that one day you might find yourself having to justify your actions, and unfortunately the only thing that you have to help you is the AFM.

It's a shame that some people have taken to emailing you, if we cant discuss these issues, how are we ever expected to learn from our mistakes?

Mutt

Hello Mutt

I know exactly what an extended segment climb is - its impractical on the 601 as I explained before as I only have 5 mins at max thrust on one engine.

I think you are correct - the answer I need to get from Bombardier, and more importantly, find a generic answer, is if the flap retraction occurs at V2+x having been all engines operating to that point, is obstacle clearance guaranteed. Thats a useful comment and you're right. My belief is that given everyone on here agrees that its ok to take the flaps up at 400 feet that the answer is yes. Otherwise, why would it be ok to take flaps up at 400 feet? The gradient you get clean at V2+x from 400 feet has to compare favourably to the one you would get at V2 flapped otherwise you couldn't do it.

The gradient will be the same if you are V2+20 clean whether you are at 400 feet or 200 feet or 600 feet so how could it not be ok?

You would always have to leave the flaps in the take off configuration until you got to 1500 feet. And that is clearly not the case - I hope we can all agree on that.

I completely get that hardly anyone on here agrees with me but thats irrelevent - lets get proper answers from manufacturers and perhaps the now muddied waters will clear. I will let you chaps know what answers I get - hey, if I'm wrong, I owe a lot of beer! If I'm right, we all get a bit of info out of this.

I think that you will make your life a lot easier if you just accept that you are talking about the CL601 ONLY :)

My one interaction with Bombardier was related to the CRJ, due to a lack of computerised software, they had a hard time validating ANY takeoff weights, so I would be extremely surprised if they can give you a proper answer related to all engine performance.

Good Luck and make mine a Guinness :)

Mutt

FAR 25.1 Applicability 'This part prescribes airworthiness standards for the issue of type certificates, and changes to those certificates, for transport category airplanes.'

In essence FAR 25 does not restrict us as pilots. It is for certification purposes and the configuration changes are to stop manufacturers from using a complex and difficult configuration change in order to certify the aircraft.

Not sure about other countries but in Australia the reg that applies to us is CAO 20.7.1B which covers planning and executing a take off. In our case we need to be able to ensure 35' obstacle clearance on departure and 50' in a turning departure.

It states: 'An aeroplane may be accelerated in level flight from V2 speed to final take-off climb speed at a height above the take-off surface that is the greater of:
(a) 400 feet; or
(b) the height necessary to achieve obstacle clearance in accordance with paragraphs 12.1 and 12.2.'

If you don't need to fly a level segment and still meet the obstacle clearance your good so far. It goes on to say:

14 AEROPLANE CONFIGURATION AND PROCEDURES
14.1 Paragraph 14.1A applies if:

(a) the manufacturer of, or the holder of the type certificate for, an aeroplane

has published advice, recommendations or guidance (the information)about the performance of the aeroplane in an emergency, unusual
operating conditions or an abnormal configuration; and
(b) the aeroplane is in the emergency, conditions or configuration.

14.1A The pilot in command of the aeroplane must take the information into account
when planning the take-off or landing of the aeroplane.

14.1B In subparagraph 14.1 (a), type certificate includes foreign type certificate

within the meaning of paragraph 21.041 (1) of the Civil Aviation Safety Regulations 1998.
14.2 Procedures to be followed consistent with this Order, including procedures
anticipating engine failure at any time between the commencement of take-off
and completion of landing, must be specified in the Operator’s Operation
Manual. The procedures so specified must be such that they can be consistently
executed in service by flight crews of average skill and they must also be such
that the take-off flight path with all engines operating is above the one-engine
inoperative take-off flight path.

How do I interpret all this? Unless the manufacturer has a specific procedure my company needs to have one and that procedure could allow the retraction of flap as soon as you reach flap retraction speed as long as you meet the obstacle clearance OEI and all engines and does not require a level acceleration below 400'.

I think the 400' for flap retraction comes from people using the same logic about keeping the configuration the same, but not updating it after 1970 when aircraft started having the performance to get higher before having to accelerate!

Tom, my comment about the flaps helping the initial climb was from a handling perspective, not a performance one. All your calculations may well be correct, but that doesn't alter the current requirement, and climbing at 190 (or other suitable speed for different types) is compliant. There is an entire thread over on techlog about whether using reduced thrust for a NADP actually increases noise levels, but it is entirely academic.

Effectively at the moment, to use a car analogy, you are saying that because my car is more efficient at 50mph in 5th gear than it is at 30mph in 3rd I should ignore the 30mph speed limit. Unfortunately, the fact that your reasoning may be correct does not make the speed limit go away!

Therefore I will continue to follow my company's procedure which is compliant with the rules.

Happy flying.

Thats very sensible biz. I think the NADP is flawed both from an aircraft handling perspective and from a noise perspective (as I mentioned, noise and vibration is my previous career and I worked for the company that made buckets of cash out of selling noise monitoring stations to airports amongst other things Airport environment management - Brüel & Kjær). There's nothing unsafe in either method (actually I think strict adherence to the letter of both NADP1 and 2 has some safety implications for aircraft like ours). I hope you agree that the subject is also worth discussion at some point and not only on here - the rulemakers need to see the arguments against the noise profiles they suggest. The issue with the NAP's is that unless you force operators to remain at full chat you have no way to prove repeat-ability in your noise samples. The maths is just too complicated if you let people do the sensible thing and climb at a high rate in a clean configuration with the power reduced because who knows what noise you make when the throttles are in any position other than max take off. They take the simple option and say "max thrust, known noise source, make the aeroplane climb at the steepest gradient we can" because anything else can't be proved.

anyway, thats another thread..

WOW. It all sounds amazingly academically anal. But then, JAA certification is kinda like that.

Bingo

it aint actually that complicated. Its simple. You can retract the flaps once the speed is correct.

If you need a level segment to achieve that speed the most common one to use is 1500 feet but you can use anything between 400 feet and the end of your single engine max thrust limit.

When you are all engines operating you can take the flaps up before 400 feet if you want because you don't need a level segment.

Mr Greendeck, thanks for that bit of legislation. I think I need to hunt around a bit more and find that written down in the northern hemisphere now! I've sent a written request to Bombardier and I'm probably going to send it to Cessna tomorrow to see if I can get some manufacturer responses. I won't bother with Hawker, they're all a bit busy..

No, you can't. But that is OK, about 10 of us here have been saying that for the last 10 pages and you, Tom seem to be the only one who still does not get it.

can you take the flaps up at 400 feet then? Is that ok?

Flaps up at 400 is perfectly acceptable unless you need an extended second segment. As to the rest, I actually mostly agree with you.

Right. Flaps up at 400 feet.

Whats your plan for climbing away from an engine failure at 400 feet (I'll save you the detail of "you've just selected flaps up and you hit a bird")

Lets just assume that you made the miracle of 400 feet, you have achieved V2+20, and you've taken the flaps up.

Whats your plan now?