What Aileron Setting Gives Spoiler Lift B737
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What Aileron Setting Gives Spoiler Lift B737
Purely research but can't find the answer on the search function, so can anyone here on the 737 enlighten me as to when the spoilers will begin to lift as the control column is turned?
I'm looking into this for the purpose of how much deflection is required for a cross wind take off but I can't find a figure in the Boeing manual other that 10 degrees...........but how many units of Aileron setting on the top of the control column is that
Many Thanks,
S.C.
I'm looking into this for the purpose of how much deflection is required for a cross wind take off but I can't find a figure in the Boeing manual other that 10 degrees...........but how many units of Aileron setting on the top of the control column is that
Many Thanks,
S.C.
Airtest limits as follows:
Classics: They should all be down at 1.6 units and be partially raised by 3.0 units.
NG's: They should all be down at 1.5 units and be partially raised by 4.0 units.
Classics: They should all be down at 1.6 units and be partially raised by 3.0 units.
NG's: They should all be down at 1.5 units and be partially raised by 4.0 units.
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On the 747 it used to be 1 div aileron trim for 5 kt crosswind component. Not sure for the 737 as it's not as clear on the control boss. I would suggest going with 'a little' (like 10 degrees) for a low crosswind, more (about 15 degrees) for a medium large crosswind, and see how that works. I don't think spoiler drag is a big problem on take-off- all the speedbrakes aren't exactly powerful even at 250 kts on a 737. A couple just floating up gently below 150 kts isn't really going to have any effect dragwise at all.
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Slight thread creep, but .....
On the B717, the FCOM says,
Having sat over the wing several times when passengering on the type, I've yet to see a spoiler deploy during any turn, even 90° turns onto final, which I'm sure are the result of more than 5° of control wheel deflection.
On the B717, the FCOM says,
For greater roll control, with more than 5 degrees of control wheel input, the flight spoilers extend a proportionate amount on the downward moving wing.
Rainboe. You said:
The FCTM states large control wheel inputs can have an adverse effect on directional control near V1 (MCG) due to additional drag of the extended spoilers....limit control wheel input to that required to keep wings level....use of excessive control wheel may cause spoilers to rise which has the effect of reducing tail clearance.... incorrect use of control wheel input will cause spoilers to extend and increase the take off distance.
And you don't think spoiler drag is a big problem on take off?
I don't think spoiler drag is a big problem on take-off- all the speedbrakes aren't exactly powerful even at 250 kts on a 737. A couple just floating up gently below 150 kts isn't really going to have any effect dragwise at all.
And you don't think spoiler drag is a big problem on take off?
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<<And you don't think spoiler drag is a big problem on take off?>>
No. I am on simulator training for the 737 now. We measured time and distance from Vmo to 220 kts speedbrakes retracted and fully extended. Distances 14/10 miles. They only made 4 miles difference and 20 seconds in the time to slow down. The 737 speedbrakes fully extended are not very effective at high speed. The effect of the speedbrakes is not great, and that is with 3 raised on each wing. Using them as spoilers to assist the aileron, 2 will rise on one wing only. How effective at creating drag in the few seconds up to 150 kts do you think 2 spoilers will be? On all the jets I've flown, with a strong crosswind on takeoff, I've needed far more than 10 degrees aileron control. The maximum I recall ever seeing is about 45 degrees, and I've never run off the end yet! It's a fact of life, you need it. Your quotation from the manual says <<limit control wheel input to that required to keep wings level>>. It does not say to limit it to avoid spoiler upfloat. the meaning is to 'avoid excessive control wheel.....blah blah'. This is in keeping with my previous experience which is 8 years 737 as well as 18 years 747.
Incidently, aileron over 10 degrees will raise the spoilers according to the Tech manual.
No. I am on simulator training for the 737 now. We measured time and distance from Vmo to 220 kts speedbrakes retracted and fully extended. Distances 14/10 miles. They only made 4 miles difference and 20 seconds in the time to slow down. The 737 speedbrakes fully extended are not very effective at high speed. The effect of the speedbrakes is not great, and that is with 3 raised on each wing. Using them as spoilers to assist the aileron, 2 will rise on one wing only. How effective at creating drag in the few seconds up to 150 kts do you think 2 spoilers will be? On all the jets I've flown, with a strong crosswind on takeoff, I've needed far more than 10 degrees aileron control. The maximum I recall ever seeing is about 45 degrees, and I've never run off the end yet! It's a fact of life, you need it. Your quotation from the manual says <<limit control wheel input to that required to keep wings level>>. It does not say to limit it to avoid spoiler upfloat. the meaning is to 'avoid excessive control wheel.....blah blah'. This is in keeping with my previous experience which is 8 years 737 as well as 18 years 747.
Incidently, aileron over 10 degrees will raise the spoilers according to the Tech manual.
Rainboe. You make some interesting points about the absence of discernable drag caused by spoilers on the take off run. If you are sure of your facts why not write to Boeing and advise them of your research results on the matter. I am sure Boeing would be most interested.
More recently I saw a report by a crew member of a B737 NG where the aircraft took off on a 7500 ft length sea level runway with a 20 knot steady crosswind. The captain used two thirds full control wheel from the start of the take off run (the captain later explained he always did this from his flying school days). Around 110 knots, if I recall correctly, the first officer noticed a marked drop in acceleration and he was immediately concerned that V1 was now meaningless. The hesitation or drag at that speed was definately noticeable according to the F/O and much more runway was used than estimated. He was convinced spoiler drag building up at the higher speed range was the culprit. All this is no problem unless Murphy's Law dictated an engine failure near V1 on the wet runway and an abort was necessary where V1 was now invalid due perceived spoiler drag. Certainly the FCTM cautionary note on extended take off distance with incorrect cross wind control wheel application rang true in this particular case.
More recently I saw a report by a crew member of a B737 NG where the aircraft took off on a 7500 ft length sea level runway with a 20 knot steady crosswind. The captain used two thirds full control wheel from the start of the take off run (the captain later explained he always did this from his flying school days). Around 110 knots, if I recall correctly, the first officer noticed a marked drop in acceleration and he was immediately concerned that V1 was now meaningless. The hesitation or drag at that speed was definately noticeable according to the F/O and much more runway was used than estimated. He was convinced spoiler drag building up at the higher speed range was the culprit. All this is no problem unless Murphy's Law dictated an engine failure near V1 on the wet runway and an abort was necessary where V1 was now invalid due perceived spoiler drag. Certainly the FCTM cautionary note on extended take off distance with incorrect cross wind control wheel application rang true in this particular case.
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Gday,
I have found that the small and recomended aileron input throughout the take off roll is sufficient up to the X-wind limits,
until you commence the rotation, then I have seen and used a seemingly LARGE amount of aileron to keep the wings level until liftoff.
I think follow the FCTM, but also you are being paid to fly the machine, so do as is required on the day.
Cheers,
Con
I have found that the small and recomended aileron input throughout the take off roll is sufficient up to the X-wind limits,
until you commence the rotation, then I have seen and used a seemingly LARGE amount of aileron to keep the wings level until liftoff.
I think follow the FCTM, but also you are being paid to fly the machine, so do as is required on the day.
Cheers,
Con
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The maximum I recall ever seeing is about 45 degrees, and I've never run off the end yet!
ANY spoiler deployment must 'spoil' the aerodynamics of the wing - lift, drag and probably both. You are in uncharted territory at that point.
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It doesn't work so well on other aeroplanes. The highly swept 747-400 wing does lift easily, and needs positive control to hold it down. I take your point that maybe the 737 doesn't need so much aileron application in a crosswind- the earlier model 737 wing is quite small whereas the 757/767/747 wings have a larger relative area and more sweep and are perhaps more affected by crosswind.
Any spoiler upfloat is not that large, limited to 2 panels, and as so much of the takeoff is below 120kts, the drag effects are IMO minimal. There is no drag penalty starting off with large aileron application and backing it off as you accelerate, which is the technique i have always used. When you feel a wing lift as I have, and it happens on certain types, you have a respect for it. It would not be sensible to have 45 degrees on at V1- I referred to that as a maximum at the start of the take-off roll.
Such 'impressions' are not awfully reliable. On a Classic 747 take-off BOM RW27, max wt. in the heat of the summer, I was shocked at the proximity of the end of the runway at the V1 call. I reported the performance as incorrect as I felt we could not have stopped. Our performance team did an analysis and wrote to me that we could have stopped with hundreds of feet to spare, and I didn't believe it. Shortly after, another of our Classics abandoned take-off in the same place, max weight, high temperature, one brake unit locked out, one reverser locked out (so corresponding one on other side unusable). They stopped, with hundreds of feet to spare, bang on calculation. So personal opinions in relation to performance are not very reliable- all that counts is those graphs!
Any spoiler upfloat is not that large, limited to 2 panels, and as so much of the takeoff is below 120kts, the drag effects are IMO minimal. There is no drag penalty starting off with large aileron application and backing it off as you accelerate, which is the technique i have always used. When you feel a wing lift as I have, and it happens on certain types, you have a respect for it. It would not be sensible to have 45 degrees on at V1- I referred to that as a maximum at the start of the take-off roll.
More recently I saw a report by a crew member of a B737 NG where the aircraft took off on a 7500 ft length sea level runway with a 20 knot steady crosswind. The captain used two thirds full control wheel from the start of the take off run (the captain later explained he always did this from his flying school days). Around 110 knots, if I recall correctly, the first officer noticed a marked drop in acceleration and he was immediately concerned that V1 was now meaningless......
Last edited by Rainboe; 13th Jun 2006 at 11:09.
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Michael 1282, thanks for the 2.5 input. Was on the line with a training captain who insisted it was 2.0 and asked me not to exceed it on take off as it would induce excessive drag and lead to a new take off distance?
To date I still can't find the figure in the FCTM other than what is stated in the Ops manual
So is that ten percent of the total amount the control wheel can turn to either side
S.C.
To date I still can't find the figure in the FCTM other than what is stated in the Ops manual
When the control wheel is displaced more than 10°, spoiler deflection is initiated
S.C.
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It's 10 degrees. That is the deflection one could use for a light crosswind, so it is obviously expected that spoiler upfloat will occur for stronger crosswinds. Boeing is suggesting not overdoing it unnecessarily. It is that last word that is generating the discussion.
Out of interest, I referred to the Bible, DP Davies' 'Handline the Biggies':
According to the 747 official company manual, that was 1 division/5kts, so a 15 kt Xwind would give you quite large deflection of the wheel, which was acceptable- hard to estimate, but I would think >20 degrees. It would seem the 737 doesn't suffer the same degree of wing lift on take-off.
Out of interest, I referred to the Bible, DP Davies' 'Handline the Biggies':
So take care when operating in crosswinds. On take-off, set in a little into-wind aileron control quite early in the take-off run whether or not you feel it is necessary, this will stop the down wind roll which will otherwise occur just before lift-off.
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Thanks guys for the info, greatly appreciate it.
BOAC, probably the best idea yours is, i'll make sure to do that next time i'm in the good seat, hope your keeping well mate?
S.C.
BOAC, probably the best idea yours is, i'll make sure to do that next time i'm in the good seat, hope your keeping well mate?
S.C.
