Use of speed brakes in flight
Join Date: Jul 2002
Location: Netherlands
Age: 71
Posts: 165
Likes: 0
Received 0 Likes
on
0 Posts
The Fokker F28 was fitted with tail mounted speedbrakes,: they could and would be used during the approach, exactly why I don't know, never flew one.
Possibly because of a non-slatted wing, thus less/not enough drag for an approach.
https://upload.wikimedia.org/wikiped..._F-28-1000.jpg
Possibly because of a non-slatted wing, thus less/not enough drag for an approach.
https://upload.wikimedia.org/wikiped..._F-28-1000.jpg
Join Date: Jun 2000
Location: last time I looked I was still here.
Posts: 4,507
Likes: 0
Received 0 Likes
on
0 Posts
They don't call it the 'Geneva lever' for nothing! ��
Ah. They were expert at LOC + GP intercept 5000' 210kts all at the same time. Testing times.
Ah. They were expert at LOC + GP intercept 5000' 210kts all at the same time. Testing times.
Not using the speed brakes when necessary is equivalent to not using the foot brake in your car. You can manage without it sometimes, but other times you need to use it - especially since you don't always know what ATC's plan and traffic flow situation is. No problem.
Join Date: Mar 2014
Location: australia
Age: 81
Posts: 207
Likes: 0
Received 0 Likes
on
0 Posts
I find it hard to understand why using spoilers to maintain a glideslope will increase fuel use.
On the slope engine is running at low power or idle. Using speed brakes will not change this. It seems that the fuel to land will be the same or less for each scenario. Of course if you land fast higher use of the reverse thrust will use more fuel.
I cannot resist this:
It seems some Captains do not like to rein in their paper waving when reigning over the cockpit. sorry........
On the slope engine is running at low power or idle. Using speed brakes will not change this. It seems that the fuel to land will be the same or less for each scenario. Of course if you land fast higher use of the reverse thrust will use more fuel.
I cannot resist this:
It seems some Captains do not like to rein in their paper waving when reigning over the cockpit. sorry........
I think the idea is managing your energy earlier on in the approach or descent, if you had of started descending earlier or slowed down earlier there would not be a need for speed brake. The fuel savings would have occurred 20 minutes prior to actually needing the speed brake
Join Date: Jul 2002
Location: Netherlands
Age: 71
Posts: 165
Likes: 0
Received 0 Likes
on
0 Posts
Harryw
You are obviously not a (heavy) jet driver. Approaches on heavy transports, but also on "lighter" fast jets like fighters are ALWAYS flown with lots of power, up to 85%.
Specific approach speeds have been chosen for many reasons: like the lowest possible with that load and flight conditions (1,3Vs) to reduce landing length, a critical factor in most jet planes. Therefore huge flap types are used (see the B747 and A380) with large deflections, creating lots of lift AND drag.
Another one is speed stability, nothing more difficult is a jet that starts creeping away from its desired approach speed (in both directions) and continues to do so. You keep on juggling the throttles, very nasty.
That can be a difficult one to attain for designers, like the B747-400 was OK with flaps at "30" but definitely more "slippery" with flaps "25". One of the reasons for the Quantas incident at Bangkok, although, like usual, more factors were involved there. https://en.wikipedia.org/wiki/Qantas_Flight_1
Jet engines, even the newer ones, still need time to accelerate out of (deep) idle. This can be critical if an immediate Go Around is needed. Carrier based planes do this to the max, as the pilots are trained to select full power upon touchdown, just to have full power if the cable is missed, needing to accelerate out of an idle range would kill them if a cable is missed (bolter).
Accepting an higher final speed because You can;t or won't decelerate is not done in jetflying. Till shortly before touchdown You fight to stick to the approach speed, but NEVER doing that by reducing power to idle. If due to turbulence or wind shear You do end up with an overshoot in speed, You are the deciding part if You GA or think You have enough stopping power on the runway in the given conditions.
Both options have killed pilots and passengers.
So if the design of the plane offers You not enough drag and end up with a too low power setting in certain conditions, like a heavy load or a slight tailwind, planes like the before mentioned F28 have an alternative use of increasing drag with speedbrakes. Specifically the tail mounted ones are less dangerous during final, as they only increase drag and do not kill lift as wing mounted ones do.
The B2 bomber uses "splitable" ailerons to create drag, however I do not know if that is used on final.
https://theaviationist.com/wp-conten...13/09/B-2A.jpg
As has been said before in this thread, it is not always Your mistake to end up with too much energy, mostly it is caused by other traffic or ATC. Not implicating it is their fault, but as they handle lots of traffic, it cannot always be done with the specific performance of ONE of their "clients" in mind.
Certain airports like Santiago de Chile have the Andes mountains block an optimum descent path, once You cleared the tops, all drag possible was needed to kill energy.
Personally I found straight in approaches the most difficult ones, especially if the traffic was light and ATC did not gave a s**t how You did it with what speed. Curved approaches offer way more options to correct both ways.
To fly an optimal descent in which You have used the kinetic energy to its max is to end up, at or just past point "D" with gear and final flaps coming down and engines spooling up to their normal approach settings. Without ending up in a rushed approach.
I was a line check pilot for a long time and witnessed many crews flying textbook descents and approaches, sometimes without any electronic help, during visual approaches.
Deciding when to crank out the next flap setting is sometimes wonderful to witness how and when that is done. Some pilots just have a wonderful "3D" insight, and are experts in using that, it was a joy to fly with those pros.
You are obviously not a (heavy) jet driver. Approaches on heavy transports, but also on "lighter" fast jets like fighters are ALWAYS flown with lots of power, up to 85%.
Specific approach speeds have been chosen for many reasons: like the lowest possible with that load and flight conditions (1,3Vs) to reduce landing length, a critical factor in most jet planes. Therefore huge flap types are used (see the B747 and A380) with large deflections, creating lots of lift AND drag.
Another one is speed stability, nothing more difficult is a jet that starts creeping away from its desired approach speed (in both directions) and continues to do so. You keep on juggling the throttles, very nasty.
That can be a difficult one to attain for designers, like the B747-400 was OK with flaps at "30" but definitely more "slippery" with flaps "25". One of the reasons for the Quantas incident at Bangkok, although, like usual, more factors were involved there. https://en.wikipedia.org/wiki/Qantas_Flight_1
Jet engines, even the newer ones, still need time to accelerate out of (deep) idle. This can be critical if an immediate Go Around is needed. Carrier based planes do this to the max, as the pilots are trained to select full power upon touchdown, just to have full power if the cable is missed, needing to accelerate out of an idle range would kill them if a cable is missed (bolter).
Accepting an higher final speed because You can;t or won't decelerate is not done in jetflying. Till shortly before touchdown You fight to stick to the approach speed, but NEVER doing that by reducing power to idle. If due to turbulence or wind shear You do end up with an overshoot in speed, You are the deciding part if You GA or think You have enough stopping power on the runway in the given conditions.
Both options have killed pilots and passengers.
So if the design of the plane offers You not enough drag and end up with a too low power setting in certain conditions, like a heavy load or a slight tailwind, planes like the before mentioned F28 have an alternative use of increasing drag with speedbrakes. Specifically the tail mounted ones are less dangerous during final, as they only increase drag and do not kill lift as wing mounted ones do.
The B2 bomber uses "splitable" ailerons to create drag, however I do not know if that is used on final.
https://theaviationist.com/wp-conten...13/09/B-2A.jpg
As has been said before in this thread, it is not always Your mistake to end up with too much energy, mostly it is caused by other traffic or ATC. Not implicating it is their fault, but as they handle lots of traffic, it cannot always be done with the specific performance of ONE of their "clients" in mind.
Certain airports like Santiago de Chile have the Andes mountains block an optimum descent path, once You cleared the tops, all drag possible was needed to kill energy.
Personally I found straight in approaches the most difficult ones, especially if the traffic was light and ATC did not gave a s**t how You did it with what speed. Curved approaches offer way more options to correct both ways.
To fly an optimal descent in which You have used the kinetic energy to its max is to end up, at or just past point "D" with gear and final flaps coming down and engines spooling up to their normal approach settings. Without ending up in a rushed approach.
I was a line check pilot for a long time and witnessed many crews flying textbook descents and approaches, sometimes without any electronic help, during visual approaches.
Deciding when to crank out the next flap setting is sometimes wonderful to witness how and when that is done. Some pilots just have a wonderful "3D" insight, and are experts in using that, it was a joy to fly with those pros.
Join Date: Jun 2000
Location: last time I looked I was still here.
Posts: 4,507
Likes: 0
Received 0 Likes
on
0 Posts
Of course if you land fast higher use of the reverse thrust will use more fuel.
And it will use even more if screw it up and make a GA.
but NEVER doing that by reducing power to idle.
An interesting sweeping comment. True, the medium/big fan engines take time to spool up again. That process needs to be started 5-10 kts before target speed is reached, if at final flap setting. Not necessarily easy to judge. B737, if already at final flap, I used to advise reducing to 40% on a gusty day as this gave instant response if thrust increase was required. That was well below stable thrust and so allowed enough to slow down and still meet 'stable criteria'. The other point about low thrust or speed brake to slow down is that some types e..g B737 do not allow speed brake >F10. If on approach and with a runaway speed I found too many pilots were hesitant to lower the gear. They were still aiming at the hotshot 500' gate and gear down at 4nm. In an ideal world, perhaps, but if you need the gear then use it. However, in the Trained Mky modern pilot world some are taught to conserve fuel at all costs and the gear down point is specified. That creates a blinkered understanding of energy management.
And it will use even more if screw it up and make a GA.
but NEVER doing that by reducing power to idle.
An interesting sweeping comment. True, the medium/big fan engines take time to spool up again. That process needs to be started 5-10 kts before target speed is reached, if at final flap setting. Not necessarily easy to judge. B737, if already at final flap, I used to advise reducing to 40% on a gusty day as this gave instant response if thrust increase was required. That was well below stable thrust and so allowed enough to slow down and still meet 'stable criteria'. The other point about low thrust or speed brake to slow down is that some types e..g B737 do not allow speed brake >F10. If on approach and with a runaway speed I found too many pilots were hesitant to lower the gear. They were still aiming at the hotshot 500' gate and gear down at 4nm. In an ideal world, perhaps, but if you need the gear then use it. However, in the Trained Mky modern pilot world some are taught to conserve fuel at all costs and the gear down point is specified. That creates a blinkered understanding of energy management.
Join Date: Jul 2002
Location: Netherlands
Age: 71
Posts: 165
Likes: 0
Received 0 Likes
on
0 Posts
RAT 5
True, at one time our management decided to lower the standard final flap setting from 30 to 25 degr. on our 747's in order to save some fuel and wear. Mind, 30 was not PROHIBITED.
Nobody really liked it, as like stated before, the speed stability was reduced, so larger speed excursions on both sides happened.
For non-747 drivers: although it does not look much, the difference in drag btn 25 and 30 is quite dramatic.
At one check flight, the crew selected the 25 setting, notwithstanding:
Max LDG wt, slight tailwind, down sloping RWY, and if my memory serves me right, one reverser U/S (so the opposite also not to be used.)
A screeching halt resulted.
The crew defended itself because that was what the management wanted.
That is a way of thinking I cannot, and refuse to, understand this kind of poor airmanship.
I really never looked a lot to my power setting during the app, after a while the throttle angle gives more than enough indications of how much oooommmph You have selected. So everybody had some kind of "arm length" one was willing to reduce N1 to, if needed.
Of course attitude, speed an V/S are the parameters to look at, so a heavy jet is basically not much more than a C172. You can land a B747 visually with only IAS, nothing more is needed. Surprisingly many runways that lack an ILS need to be flown like that.
(OK, I am of a pre-GPS approach generation.....)
True, at one time our management decided to lower the standard final flap setting from 30 to 25 degr. on our 747's in order to save some fuel and wear. Mind, 30 was not PROHIBITED.
Nobody really liked it, as like stated before, the speed stability was reduced, so larger speed excursions on both sides happened.
For non-747 drivers: although it does not look much, the difference in drag btn 25 and 30 is quite dramatic.
At one check flight, the crew selected the 25 setting, notwithstanding:
Max LDG wt, slight tailwind, down sloping RWY, and if my memory serves me right, one reverser U/S (so the opposite also not to be used.)
A screeching halt resulted.
The crew defended itself because that was what the management wanted.
That is a way of thinking I cannot, and refuse to, understand this kind of poor airmanship.
I really never looked a lot to my power setting during the app, after a while the throttle angle gives more than enough indications of how much oooommmph You have selected. So everybody had some kind of "arm length" one was willing to reduce N1 to, if needed.
Of course attitude, speed an V/S are the parameters to look at, so a heavy jet is basically not much more than a C172. You can land a B747 visually with only IAS, nothing more is needed. Surprisingly many runways that lack an ILS need to be flown like that.
(OK, I am of a pre-GPS approach generation.....)
Last edited by Double Back; 22nd May 2016 at 18:26. Reason: slight editorial change
Join Date: Jun 2000
Location: last time I looked I was still here.
Posts: 4,507
Likes: 0
Received 0 Likes
on
0 Posts
Your story is scary. Management is for managing. Airmanship is for operating aeroplanes as the situation demands. I did have some interesting discussions with young F/O's who insisted on landing F30 (B737) disconnecting auto brakes with large feet and pulling FULL reverse to make a turn off; because F30 was company standard?????? The idea that some runways and ambient conditions cause different thinking on the day was a surprise. Unless F40 was specified in the airfield brief there seemed be great reluctance to use it. GRO RW20 downhill, wet, slight tailwind and still a F30 VMC 500' gate was briefed. Hm?????
Join Date: Feb 2000
Location: London, UK
Age: 64
Posts: 103
Likes: 0
Received 0 Likes
on
0 Posts
Humble passenger here. Am I correct in thinking speed brakes are always used on E170 / E190 and 146/RJ into LCY - steep approach and all that. On the E170/E190 it does create noticeable vibration.
Join Date: Jun 2000
Location: last time I looked I was still here.
Posts: 4,507
Likes: 0
Received 0 Likes
on
0 Posts
Broadening the discussion: what opinions about the use of full or partial speed brake application? I know the recommendation is often full or nothing. Sometimes I found full caused too much rumbling; and having sat amongst nervous pax it felt un-nerving. Thus I usually used up to the rumble strip deflection. Other scenarios were when I was high approaching the GP from above I used SpdBk to give me a ROD to reach GP intercept at correct speed and ALT without any level off, and in a smooth manner. The diversity of reactions was interesting including those of 'plain wrong'. One company had an SOP for everything and there it was written all or nothing. I used to hate those straight-jacket restrictions that left no option for technique/finesse & best for the moment decisions.
Join Date: Jul 2002
Location: Netherlands
Age: 71
Posts: 165
Likes: 0
Received 0 Likes
on
0 Posts
When the need for SB was expected we were advised to warn the pax about the rumble, which on a B747 was clearly noticeable and audible.
(BTW the same if the gear was to be extended at a higher than normal speed)
It was left to the PF if they were opened full or partly. At about 3/4 of lever travel there was an area with more friction. If not dealt with cautious, the lever would slam to the stop and pop up the panels too fast, which was not quite pax comfort wise.
In general it was known that as of 250 KTS the effect was far less as above 300 KTS, and as You were in the flap/LE range, extending those was more efficient.
I once ended up about 60Nm from the destination, before getting the descent clearance, so heck, we made an "emergency descent" with full SB and 350 Kts, all the way down to 1500' to downwind (over water), levelling off and decelerating with SB open, cranking flaps and gear while turning base, rolling out on final for a stabilised visual.
Yes, it was StMaarten, (but it wasn't me that made the famous low app
)
(BTW the same if the gear was to be extended at a higher than normal speed)
It was left to the PF if they were opened full or partly. At about 3/4 of lever travel there was an area with more friction. If not dealt with cautious, the lever would slam to the stop and pop up the panels too fast, which was not quite pax comfort wise.
In general it was known that as of 250 KTS the effect was far less as above 300 KTS, and as You were in the flap/LE range, extending those was more efficient.
I once ended up about 60Nm from the destination, before getting the descent clearance, so heck, we made an "emergency descent" with full SB and 350 Kts, all the way down to 1500' to downwind (over water), levelling off and decelerating with SB open, cranking flaps and gear while turning base, rolling out on final for a stabilised visual.
Yes, it was StMaarten, (but it wasn't me that made the famous low app
)
Join Date: Jan 2006
Location: US
Posts: 2,205
Likes: 0
Received 0 Likes
on
0 Posts
Remember the good old days, when guys would descend 30 miles early to make sure they didn't use the speed brake? Or put the flaps out at the highest speeds allowed so they wouldn't use the speed brake? Or lower the gear at high speed, miles early, just so they wouldn't use the speed brake?
Gas wasted? Noise? Beating up the airplane? Not my problem! I didn't use the speed brakes and that's what counts! <sigh>
Gas wasted? Noise? Beating up the airplane? Not my problem! I didn't use the speed brakes and that's what counts! <sigh>
Join Date: Jul 2002
Location: Netherlands
Age: 71
Posts: 165
Likes: 0
Received 0 Likes
on
0 Posts
I also remember (on the DC10) which was restricted in SB use to clean config. only (if I recall correctly), it was warned that the combined use was said to be like "stripping the bird of its feathers". We all thought it would stall vicious if You would forget about this!
It was quite a shock to migrating ex DC10 pilots that the good ole 747-400 the SB was allowed till and including flap 20 setting, which features full LE extension and already all flap panels out.
It was quite a shock to migrating ex DC10 pilots that the good ole 747-400 the SB was allowed till and including flap 20 setting, which features full LE extension and already all flap panels out.
@ misd-agin, good post. Like I said, one can compare using speed brakes to using the brakes on your car; you can sometimes manage without using them, but you usually have to make compromises in other areas, eg, in the car example; separation from the vehicle in front.
It is nice not to have to use speed brakes, but when you need to, why is it such a big deal with some folk?
A Cap once told me not to use speed brake in a 330 - I had barely cracked them open, so there was no vibration or rumble - just to prevent getting high on profile by adding a few hundred feet per minute to my V/S. Right, I will teach you I thought, so I did the whole descent and approach and intercept without touching the speed brakes from that point on. We were cut in a bit by ATC and everything was at the far end of just reasonable the whole way down. I managed it, but you should have seen him squirm!
It is nice not to have to use speed brakes, but when you need to, why is it such a big deal with some folk?
A Cap once told me not to use speed brake in a 330 - I had barely cracked them open, so there was no vibration or rumble - just to prevent getting high on profile by adding a few hundred feet per minute to my V/S. Right, I will teach you I thought, so I did the whole descent and approach and intercept without touching the speed brakes from that point on. We were cut in a bit by ATC and everything was at the far end of just reasonable the whole way down. I managed it, but you should have seen him squirm!
Join Date: Jan 2006
Location: US
Posts: 2,205
Likes: 0
Received 0 Likes
on
0 Posts
I see enough guys that know they're going to need speed brakes but instead of using partial speed brakes, which can be unnoticeable, they wait until the last moment and 'light switch' the speed brakes - Bam! Full speed brakes, Bam! Immediate retraction! Done! Comfort? Enjoyment? Who cares!
I pity their wives....
I pity their wives....
Join Date: Jun 2000
Location: last time I looked I was still here.
Posts: 4,507
Likes: 0
Received 0 Likes
on
0 Posts
Not using SB? The reverse side of the coin are the hot-shots who have a perfect VNAV PTH to GP intercept. They are on profile with 250/100. They then ask for >250 below 10. ATC agree and continue with radar vectors. Guarantee they either ask for F1 at limit speed or have to use SB's. The 1st is refused and at the 2nd my eyebrows are raised in questioning.
In answer to the 1st I remind what FCTM says about flaps as speed brakes (not) and the raised eyebrows asked the question "do you accelerate towards red traffic lights?" The runway = landing & requires you to lose 40% of your speed, so why accelerate? Blank stares!
In answer to the 1st I remind what FCTM says about flaps as speed brakes (not) and the raised eyebrows asked the question "do you accelerate towards red traffic lights?" The runway = landing & requires you to lose 40% of your speed, so why accelerate? Blank stares!
