Better Perf during rolling takeoff?
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Better Perf during rolling takeoff?
Wich aircrafts get better performance if using rolling TKF?
What i have heard the A330 get's better...not sure if thats true or not.
How is it with the A318/319/320/321? And the Boeings?
Is there another aircraft except the 330 thats get better perf?
What i have heard the A330 get's better...not sure if thats true or not.
How is it with the A318/319/320/321? And the Boeings?
Is there another aircraft except the 330 thats get better perf?
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The primary reasons for rolling takeoff have to do with engine life: Less risk of FOD or erosive particle ingestion, and longer warmup time leading to hot section preservation.
In most cases the takeoff performance difference is very small.
In most cases the takeoff performance difference is very small.
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A330
On FCOM 3, TO section the only note says : take off roll is permitted.
No specs on FCTM.
FCTM says that thrust usually reaches the TO value around 60Kts, so performing a rolling TO the same TO thrust should be reached a bit earlier.
I guess the reason(s) for a rolling TO are explained by barit1, for buses and no.
No specs on FCTM.
FCTM says that thrust usually reaches the TO value around 60Kts, so performing a rolling TO the same TO thrust should be reached a bit earlier.
I guess the reason(s) for a rolling TO are explained by barit1, for buses and no.
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The “trade-off” comes in the exchange of distance for kinetic energy. If you make a 90-degree turn to align with the runway before adding power, you get a bit more concrete in front of you, but you start with zero kinetic energy. If you turn the corner with some forward movement you keep a bit of kinetic energy but you sacrifice a bit of distance to keep it.
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FE Hoppy
"Power against brakes will always give better perf than rolling. With rolling you are using TODA before you have take off thrust."
Not necessarily.
Take the extreme case of a high speed taxiway entry onto a runway. If this is the only entry to the t/o runway and you are doing 40 - 50 knots before you hit the centre line, in a nice gradual turn, are you going to stop the aircraft again, apply power etc., then release the brakes?
My argument is this. If the aircraft is moving then keep it moving and introduce the power for t/o, provided you have been cleared for take off of course.
"Power against brakes will always give better perf than rolling. With rolling you are using TODA before you have take off thrust."
Not necessarily.
Take the extreme case of a high speed taxiway entry onto a runway. If this is the only entry to the t/o runway and you are doing 40 - 50 knots before you hit the centre line, in a nice gradual turn, are you going to stop the aircraft again, apply power etc., then release the brakes?
My argument is this. If the aircraft is moving then keep it moving and introduce the power for t/o, provided you have been cleared for take off of course.
Disagree with the power against brakes club, turn on as close to the end of the runway as you can get, but keep rolling, keep the momentum going and get the power up smartish.
Momentum is valuable, combine that with rapid thrust advance and you will always use less runway.
Momentum is valuable, combine that with rapid thrust advance and you will always use less runway.
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Here's a note from an EASA AFM near me:
NOTE: For rolling takeoffs, performance data is valid from the point
where takeoff thrust is achieved.
So unless your rolling take off is from a taxiway that allows you to acheive TO thrust at the threshold or at the point at the end of the alignment allowance considered in your calculation then beware! If the stopway doesn't get you the Judge may!!
NOTE: For rolling takeoffs, performance data is valid from the point
where takeoff thrust is achieved.
So unless your rolling take off is from a taxiway that allows you to acheive TO thrust at the threshold or at the point at the end of the alignment allowance considered in your calculation then beware! If the stopway doesn't get you the Judge may!!
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They are being very conservative in that NOTE, probably because it's cheaper than actually doing the flight test, AND because pilot technique introduces some variation.
Think of it this way: On a rolling takeoff, at the point takeoff power is reached, you've already gained 30-40 kt. speed. On a static runup, the equivalent point is ZERO kt. Applying the above NOTE, actual performance will be BETTER than a static TO.
(PS: on the SE overpowered taildragger I'm used to flying, running up to TO power then releasing the brakes is a sure recipe for a groundloop - assuming you didn't dig the nose in first!
)
Think of it this way: On a rolling takeoff, at the point takeoff power is reached, you've already gained 30-40 kt. speed. On a static runup, the equivalent point is ZERO kt. Applying the above NOTE, actual performance will be BETTER than a static TO.
(PS: on the SE overpowered taildragger I'm used to flying, running up to TO power then releasing the brakes is a sure recipe for a groundloop - assuming you didn't dig the nose in first!
)
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I think the point is that in the time the engines are spooling up the acceleration rate is less than had they been at TO thrust from the start, so the ground roll to that point( the point where TO thrust is set and the two cases reach the same speed) MAY be longer or shorter depending on the entry speed for the rolling example. Unless you are prepared to give minimum threshold crossing speeds I'm not sure how you could realistically predict the initial ground roll distance up to the point where TO thrust is set and therefore calculate the remaining acceleration.
The Aft limit of the CG envelope can be limited by brake release tip up to ensure no probs with setting thrust but I agree this doesn't apply to a tail dragger.
The Aft limit of the CG envelope can be limited by brake release tip up to ensure no probs with setting thrust but I agree this doesn't apply to a tail dragger.
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Rolling takeoff...? Not for me...
If I have a takeoff at a weight where limited by runway...
I line up the airplane (full length, when through that argument a couple of days ago).
No inter-sex-ion for me.
Line up, set brakes, spool up engines, start roll, full thrust as soon as possible.
xxx
What for a rolling takeoff...?
Do you like to give sideload "Gs" to your cabin tail passengers...?
So to avoid that, takes you 1,000 ft of wasted runway to get to full thrust.
xxx
I know many of you fly 737 and 320s... A 10,000 ft long runway is plenty.
You certainly have enough for rolling takeoff and do 3 touch and goes...
But, my young friends, if the runway is 5,500 feet long, hold the brakes, then spool your engines.
xxx
Better performance with rolling takeoff...? What vocabulary is that...?
Do you have radial tyres for better cornering...?
Happy contrails
I line up the airplane (full length, when through that argument a couple of days ago).
No inter-sex-ion for me.
Line up, set brakes, spool up engines, start roll, full thrust as soon as possible.
xxx
What for a rolling takeoff...?
Do you like to give sideload "Gs" to your cabin tail passengers...?
So to avoid that, takes you 1,000 ft of wasted runway to get to full thrust.
xxx
I know many of you fly 737 and 320s... A 10,000 ft long runway is plenty.
You certainly have enough for rolling takeoff and do 3 touch and goes...
But, my young friends, if the runway is 5,500 feet long, hold the brakes, then spool your engines.
xxx
Better performance with rolling takeoff...? What vocabulary is that...?
Do you have radial tyres for better cornering...?
Happy contrails
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Ref the A330, RR Trent 700 powered, the system used for acceleration on T/O is called, Modified Engine Acceleration Schedule for Take Off (or MEASTO for short). This is what limits engine thrust to below take-off until the correct groundspeed is reached (which I think is the quoted 60 knots).
The reason the Trent 700 needs this, is because it had a tendency to surge if the throttles were applied judiciously before a good forward speed was reached.
Regards,
N1 Vibes
The reason the Trent 700 needs this, is because it had a tendency to surge if the throttles were applied judiciously before a good forward speed was reached.
Regards,
N1 Vibes
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Thinks: "How on Earth can they run T#700 full bore on the bloody test bench, then?" 
(unless, of course, the collossal concrete containment cubicle is on wheels...)
(unless, of course, the collossal concrete containment cubicle is on wheels...
)
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My understanding of the Boeing B737NG takeoff technique is that it really doesn't make much difference if it's done efficiently, and in the rolling takeoff case, the delay in advancing the thrust from the initial setting is no longer than approximately 2 seconds!
Cheers...FD...
Cheers...FD...
If you are trying to use the minimum runway why would you want to accelerate all that weight from a dead stop, when you can have full thrust and 10-20 knots already 'in the bag' at roughly the same point.
You don't need to make a Formula one turn onto the runway either and you certainly don't need '1000 feet' to line up.
The difference in runway used to line up is minimal (if you do it right) and most modern engines are at full chat in seconds.
It's a different matter when ATC 'forces' you into position and hold on a limiting runway.Then I would set full power before releasing the brakes (or start the roll when they cannot hold the aircraft any longer)
Whichever technique you decide to use choose one ! I have sat in the back on the runway as power is increased while the brakes are dragging with the aircraft in motion for hundreds of feet !
Not exactly sure what they were trying to do but that is definitely the worst of both worlds
You don't need to make a Formula one turn onto the runway either and you certainly don't need '1000 feet' to line up.
The difference in runway used to line up is minimal (if you do it right) and most modern engines are at full chat in seconds.
It's a different matter when ATC 'forces' you into position and hold on a limiting runway.Then I would set full power before releasing the brakes (or start the roll when they cannot hold the aircraft any longer)
Whichever technique you decide to use choose one ! I have sat in the back on the runway as power is increased while the brakes are dragging with the aircraft in motion for hundreds of feet !
Not exactly sure what they were trying to do but that is definitely the worst of both worlds
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Then I would set full power before releasing the brakes (or start the roll when they cannot hold the aircraft any longer)
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rolling takeoff and intersection
Rolling takeoff... well asper FOBN ... understanding setting of takeoff thrust....
engine accelaration depends upon the rate of setting the thrust levers to the flex or toga detent... i.e if we ram it to toga... engine will still accelerate at the max persmisseble rate of the FADEC as oppose to slowly easing the engine up to takeoff thrust and not using the fadec control optimally...( ramming the thrust lever is not implied .. jus a matter or argument)so u can eat up runway even from a complete stop if ur not prompt enough to set the takeoff thrust...
so if u think that ur using up too much runway doing a rolling takeoff.. well i disagree... with the FBW.. NSW u can make a very smooth transition from a taxing turn to a rolling takeoff.. and about the g's
well ever felt the g's when u set TOGA thrust when taking off?
and about intersection takeoff... well to each his own.. but sometimes its better but most of the time its not..
engine accelaration depends upon the rate of setting the thrust levers to the flex or toga detent... i.e if we ram it to toga... engine will still accelerate at the max persmisseble rate of the FADEC as oppose to slowly easing the engine up to takeoff thrust and not using the fadec control optimally...( ramming the thrust lever is not implied .. jus a matter or argument)so u can eat up runway even from a complete stop if ur not prompt enough to set the takeoff thrust...
so if u think that ur using up too much runway doing a rolling takeoff.. well i disagree... with the FBW.. NSW u can make a very smooth transition from a taxing turn to a rolling takeoff.. and about the g's
well ever felt the g's when u set TOGA thrust when taking off?
and about intersection takeoff... well to each his own.. but sometimes its better but most of the time its not..
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Rolling takeoffs are recommended in my company on 737s (classic and NG).
The relevant text from the FCOM:
The relevant text from the FCOM:
A rolling takeoff procedure is recommended for setting takeoff thrust. It expedites takeoff and reduces risk of foreign object damage or engine surge/stall due to a tailwind or crosswind.
Rolling takeoffs are accomplished in two ways:
• If cleared for takeoff prior to or while entering the runway, maintain normal taxi speed. When the airplane is aligned with the runway centerline ensure the nose wheel steering wheel is released and the LHS applies takeoff thrust by advancing the thrust levers to just above idle (40%N1). Allow the engines to stabilize momentarily then promptly advance the thrust levers to takeoff thrust (autothrottle TO/GA). There is no need to stop the airplane prior to adding thrust.
• If holding in position on the runway, ensure the nose wheel steering wheel is released, release brakes and then apply takeoff thrust as described above.
Note: Brakes are not normally held with thrust above idle unless a static run-up is required in icing conditions.
Rolling takeoffs are accomplished in two ways:
• If cleared for takeoff prior to or while entering the runway, maintain normal taxi speed. When the airplane is aligned with the runway centerline ensure the nose wheel steering wheel is released and the LHS applies takeoff thrust by advancing the thrust levers to just above idle (40%N1). Allow the engines to stabilize momentarily then promptly advance the thrust levers to takeoff thrust (autothrottle TO/GA). There is no need to stop the airplane prior to adding thrust.
• If holding in position on the runway, ensure the nose wheel steering wheel is released, release brakes and then apply takeoff thrust as described above.
Note: Brakes are not normally held with thrust above idle unless a static run-up is required in icing conditions.
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I've flown a number of Boeings and in each one Boeing have recommended the rolling take off if permissible, if you are runway limited then I would suggest it isn't permissible?