Use of speedbrakes in turbulence
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Use of speedbrakes in turbulence
Could any of you instructors out there comment on the use of speedbrakes in conditions of severe turbulence at high altitude.
Is it adviseable to use them to prevent speed overrun or potentially hazardous in a possible upset situation.Tks.
Is it adviseable to use them to prevent speed overrun or potentially hazardous in a possible upset situation.Tks.
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The Lockheed L1011 TriStar-500 had ACS, "active control system," that would partially deploy "speed brakes," also known as "spoilers," to dampen wing flutter during turbulence. The TriStar also used DLC, "direct lift control," a partial, variable, deployment of spoilers during approach in the landing configuration to help maintain continuous body angle.
The use of manual speed brakes during turbulence is not an operational procedure. The autopilot by itself will handle light to moderate turbulence without disconnecting. In severe turbulence most autopilots have a CWS, "control wheel steering," mode, or equivalent, that would assist the pilot to manually fly the airplane by augmenting manual control inputs.
The use of manual speed brakes during turbulence is not an operational procedure. The autopilot by itself will handle light to moderate turbulence without disconnecting. In severe turbulence most autopilots have a CWS, "control wheel steering," mode, or equivalent, that would assist the pilot to manually fly the airplane by augmenting manual control inputs.
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i would say forget about it, too risky. first and foremost maintain your attitude, straight and level. try and keep throttle movement to a minimum, speed will be irratic but you don't want to intentionally over speed or stall it, if any thing keep speed up. descent to a lower level will help increase your envelope.
any body else wish to add....
any body else wish to add....
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Originally Posted by PRNAV1
i would say forget about it, too risky.... if any thing keep speed up.
I would say, if anything, FOLLOW YOUR OPERATIONS MANUAL guidance, or failing that, manufacturers recommendations. Not all aeroplane types are the same, mine for instance requires me to SLOW DOWN in severe turbulence, not 'if anything keep speed up'.
Be careful taking generalised info to use operationally. This can be very dangerous. Ask your trainers IN YOUR COMPANY if you can't find the answer having looked in your manuals.
Safe flying.
PP
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I would say, if anything, FOLLOW YOUR OPERATIONS MANUAL guidance, or failing that, manufacturers recommendations. Not all aeroplane types are the same, mine for instance requires me to SLOW DOWN in severe turbulence, not 'if anything keep speed up'.
but as you say, follow your SOP's. they're there for a reason
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Originally Posted by PRNAV1
Fair enough. but lets just say you've slowed down, you now encounter severe turb and your lower speed is not helping. you can't slow down anymore and the last thing you want is to stall. all i'm saying is i'd rather be over speed then under speed....
1. See if I can get out of the turbulence. and;
2. Increase my speed margins.
CWS where fitted is very useful as you mention, disconnecting the autothrust can also help WHERE YOUR OPS/ MANUFACTURER APPROVES. So, trying to keep it to general guidance that applies to ALL types what can we offer?
1. Fly the recommend Turbulent Air Penetration Speed.
2. Ask ATC of known turbulence, levels and duration. Report your turbulence to them CORRECTLY (how many times have you heard 'moderate turbulence' and infact it's continuous light chop)!!
3. Descend to a lower level (bear in mind MFA, ISA deviations in temperature and windspeed in mountainous areas).
4. Try to fly a constant attitude and don't chase the airspeed.
5. Strap your full harness on, stow any loose articles.
6. Delay your 'ding, dong' for tea.....
7. I always speak to the crew and gain their perception, especially at the rear galley where light chop can feel terrible to them. Liase with the No.1, if it's marginal over seat belt use you could reach a compromise (they might want the belts on, but still be able to move around the cabin themselves).
8. If safety will be compromised AT ALL (bear in mind old infirm pax who might be planning a trip to the bathroom), then put the belts on. Again, worth involving your CC in this decision (even if it's belts on first and then a call, at an appropriate time; which may not arise in severe turbulence for quite a while).
9. Consider a PA to calm what may well be extremely frightened passengers.
10. All that said, AVIATE, NAVIGATE, COMMUNICATE.
Anyone else?
PP
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Totally agree PP. glad to hear you actually take CC into consideration. Seems like you've taken the extra effort to cover all areas other than your own compfort.
iI the original question needed answering, you've answerd in full.
happy flying.
iI the original question needed answering, you've answerd in full.
happy flying.
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Think le premier's question was: do you use speedbrakes to get to turb penetration speed?
My answer would be: NO! Stall margin is reduced with speedbrakes and the wing is stressed more.
My answer would be: NO! Stall margin is reduced with speedbrakes and the wing is stressed more.
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Originally Posted by sarah737
Think le premier's question was: do you use speedbrakes to get to turb penetration speed?
My answer would be: NO! Stall margin is reduced with speedbrakes and the wing is stressed more.
My answer would be: NO! Stall margin is reduced with speedbrakes and the wing is stressed more.
Is it adviseable to use them to prevent speed overrun or potentially hazardous in a possible upset situation.
In relation to an unusual attitude recovery
Nose Low, Wings Level
In a situation where the airplane pitch attitude is unintentionally more than 10
degrees nose low and going lower, the airspeed is increasing rapidly. A pilot would likely reduce thrust and extend the speedbrakes. Thrust reduction causes an additional nose-down pitching moment. Speedbrake extension causes a nose-up pitching moment, an increase in drag, and a decrease in lift for the same angle of attack. At airspeeds well above VMO/MMO, the ability to command a nose-up pitch rate with elevator may be reduced because of the extreme aerodynamic loads on the elevator.
Again, it is necessary to maneuver the airplane's flight path back toward the
horizon. At moderate pitch attitudes, applying nose-up elevator, reducing thrust, and extending speedbrakes, if necessary, changes the pitch attitude to a desired range.
In a situation where the airplane pitch attitude is unintentionally more than 10
degrees nose low and going lower, the airspeed is increasing rapidly. A pilot would likely reduce thrust and extend the speedbrakes. Thrust reduction causes an additional nose-down pitching moment. Speedbrake extension causes a nose-up pitching moment, an increase in drag, and a decrease in lift for the same angle of attack. At airspeeds well above VMO/MMO, the ability to command a nose-up pitch rate with elevator may be reduced because of the extreme aerodynamic loads on the elevator.
Again, it is necessary to maneuver the airplane's flight path back toward the
horizon. At moderate pitch attitudes, applying nose-up elevator, reducing thrust, and extending speedbrakes, if necessary, changes the pitch attitude to a desired range.
Effect of Speedbrakes
For any airspeed, the angle of attack is higher with speedbrakes up. This increases initial buffet speed and stick shaker speed but has a lesser effect on actual stall speed.
For any airspeed, the angle of attack is higher with speedbrakes up. This increases initial buffet speed and stick shaker speed but has a lesser effect on actual stall speed.
That said, I stand to be corrected by someone more in the know and stress that this is my info based on the 737 Classic.
PP
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A fundamental misconception about airspeed during turbulence is that it should never be the primary parameter of reaction. Flying attitude and maintaining wings level should be primary. It is never advisable to "chase" airspeed or altitude during an upset.
The Mach meter will roll forward and backwards during turbulence and its indication is not accurate because pitot and static ports are affected by the associated shear forces of turbulence. This is quite obvious as an airplane cannot physically change from M.84 indication to M.88 indication and reverse in 2 or 3 seconds. Most inexperienced pilots get flustered by instantaneous, momentary high Mach indications and immediately make large thrust reductions, only to realize later that the airspeed has dropped well below minimum [long range] cruise Mach.
In moderate or severe turbulence it is advisable to disconnect auto throttles and maintain speed and fly only attitude, with less emphasis on "chasing" altitude and airspeed. It is not advisable to engage speed brakes nor to retrim the stabilizer, nor to make any sudden or large control surface inputs.
The Mach meter will roll forward and backwards during turbulence and its indication is not accurate because pitot and static ports are affected by the associated shear forces of turbulence. This is quite obvious as an airplane cannot physically change from M.84 indication to M.88 indication and reverse in 2 or 3 seconds. Most inexperienced pilots get flustered by instantaneous, momentary high Mach indications and immediately make large thrust reductions, only to realize later that the airspeed has dropped well below minimum [long range] cruise Mach.
In moderate or severe turbulence it is advisable to disconnect auto throttles and maintain speed and fly only attitude, with less emphasis on "chasing" altitude and airspeed. It is not advisable to engage speed brakes nor to retrim the stabilizer, nor to make any sudden or large control surface inputs.
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Well now Glueball, it is clear you never operated the Lockheed TriStar -500, as your description is just 'slightly' off base.
ACS controlled the ailerons, to increase wing bending relief, and MDLC (maneuvering direct lift control) deployed certain spoiler sections with the flaps fully retracted to achieve speed (overspeed) control, at altitude.
And yes, even in turbulence, as well, as some here might think unwise.
Both systems completely automatic, no pilot input required.
These two systems (ACS & MDLC) were not found on standard body TriStars, but were fitted to the -500, for the following reasons:
ACS, to increase wing bending relief, to cater for the heavier weight of the -500 model, with minimal wing structure changes, and..
MDLC, for one reason only.
The British required it fitted to the -500 model to be accepted on the British register (aircraft certification requirement).
Lockheed, way ahead of its conpetitors, in advanced aircraft systems design.
Nice ride, too...
ACS controlled the ailerons, to increase wing bending relief, and MDLC (maneuvering direct lift control) deployed certain spoiler sections with the flaps fully retracted to achieve speed (overspeed) control, at altitude.
And yes, even in turbulence, as well, as some here might think unwise.
Both systems completely automatic, no pilot input required.
These two systems (ACS & MDLC) were not found on standard body TriStars, but were fitted to the -500, for the following reasons:
ACS, to increase wing bending relief, to cater for the heavier weight of the -500 model, with minimal wing structure changes, and..
MDLC, for one reason only.
The British required it fitted to the -500 model to be accepted on the British register (aircraft certification requirement).
Lockheed, way ahead of its conpetitors, in advanced aircraft systems design.
Nice ride, too...
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411A
I'm fairly sure all British reg. L-1011's had DLC but the ACS was deactivated, certainly the -1's,-50's, 200's and 500's that I flew, had DLC.
Lovely aircraft but apart from the 500, all were underpowered.
I'm fairly sure all British reg. L-1011's had DLC but the ACS was deactivated, certainly the -1's,-50's, 200's and 500's that I flew, had DLC.
Lovely aircraft but apart from the 500, all were underpowered.
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Skiesfull,
Well, it depends.
Altho all L10's were fitted with DLC, only the -500 models were fitted with MDLC.
These are completely different animals.
While DLC was activated when the flap HANDLE was selected beyond 30 degrees, and was designed for accurate pitch control during the approach phase, MDLC, using some of the same spoiler panels, was used in cruise only, for the overspeed condition.
Also, as I have flown several ex-BA -500's, the ACS continued to be active, for if it was not, inflight weight penalties were imposed.
Likewise for MDLC, inflight weight penalties if not serviceable.
Now, as to the 'underpowered' issue.
While it is true that the -1, -50, and -100 models fitted with the -22B engine could have used more power, the -200's, and -250's fitted with the -524B02 and -524B402 engines were VERY good performers, and I have a lot of hours in these machines.
TriStar...one fine aeroplane.
An oldie but a goodie.
Well, it depends.
Altho all L10's were fitted with DLC, only the -500 models were fitted with MDLC.
These are completely different animals.
While DLC was activated when the flap HANDLE was selected beyond 30 degrees, and was designed for accurate pitch control during the approach phase, MDLC, using some of the same spoiler panels, was used in cruise only, for the overspeed condition.
Also, as I have flown several ex-BA -500's, the ACS continued to be active, for if it was not, inflight weight penalties were imposed.
Likewise for MDLC, inflight weight penalties if not serviceable.
Now, as to the 'underpowered' issue.
While it is true that the -1, -50, and -100 models fitted with the -22B engine could have used more power, the -200's, and -250's fitted with the -524B02 and -524B402 engines were VERY good performers, and I have a lot of hours in these machines.
TriStar...one fine aeroplane.
An oldie but a goodie.
Last edited by 411A; 3rd Feb 2006 at 14:18.
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411A: Yes, it's been many years since my last encounter with this wonderful ladies' airplane. My L10 systems knowledge had been blurred by other airplanes' sytems.
Anyway, thanks for the correction. It's always a pleasure taxiing past those graceful birds at JED as they always come to life during the Hadj. ...Air Rum, Air Universal, StarJet, StarGate, StarAir...etc.
Anyway, thanks for the correction. It's always a pleasure taxiing past those graceful birds at JED as they always come to life during the Hadj. ...Air Rum, Air Universal, StarJet, StarGate, StarAir...etc.
