Gulfstream IV in Bedford MA
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why were the buckets closed in all the pictures.
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why were the buckets closed in all the pictures.
One possibility for this is that when the gear came off, the nutcracker system went into air mode, T/R's would then stow as they slowed down.
mutt, I would agree with this scenario as well.
The consequences of this being that the engines would continue to now produce forward thrust, driving the aircraft on it's belly across the grass and into the gully.
why were the buckets closed in all the pictures.
One possibility for this is that when the gear came off, the nutcracker system went into air mode, T/R's would then stow as they slowed down.
mutt, I would agree with this scenario as well.
The consequences of this being that the engines would continue to now produce forward thrust, driving the aircraft on it's belly across the grass and into the gully.
Good Suggestion
That seems like a good possibility.
As a guess, it looks like they had a fair amount of forward thrust after going off the end and shearing the gear.
As a guess, it looks like they had a fair amount of forward thrust after going off the end and shearing the gear.
Just curious
Just wondering. It's been a long time since my Gulfstream days.
If they were attempting full reverse thrust, and the nutcracker failed (due to gear being sheared, or otherwise), would the reverser's stow with the levers still up?
I seem to recall the G-III had a reverser restow switch, (In case of an inflight deployment), but I think the G-IV had a much improved system, which eliminated that switch.
I notice some skid marks in one of the pictures.
I wonder if the PF pulled the emergency brake handle, which has no anti-skid protection.
Thanks for any input.
If they were attempting full reverse thrust, and the nutcracker failed (due to gear being sheared, or otherwise), would the reverser's stow with the levers still up?
I seem to recall the G-III had a reverser restow switch, (In case of an inflight deployment), but I think the G-IV had a much improved system, which eliminated that switch.
I notice some skid marks in one of the pictures.
I wonder if the PF pulled the emergency brake handle, which has no anti-skid protection.
Thanks for any input.
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would the reverser's stow with the levers still up?
which eliminated that switch.
I would go to full flaps
You are correct
I found an old G-IV checklist and the "Thrust reverser emergency stow switch" is on the before start checklist.
I guess I was thinking about another model.
Thanks for your response.
I guess I was thinking about another model.
Thanks for your response.
Last edited by Old Boeing Driver; 6th Jun 2014 at 21:39. Reason: Incorrect statment
@Mutt
Any idea why they would be doing a flaps 10 take off on a 7,000 foot runway at 8C and almost sea level?
A guess would be a 12,000 pound fuel load, and maybe a 1,000 pound payload for guessing at the T/O weight. Maybe 57-58,000 pounds at T/O
Thanks for your response.
A guess would be a 12,000 pound fuel load, and maybe a 1,000 pound payload for guessing at the T/O weight. Maybe 57-58,000 pounds at T/O
Thanks for your response.
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Quote:
would the reverser's stow with the levers still up?
Yes, at around 60 Kts.
Believe flight manual says IF flaps greater than 22 and BOTH wheels spin up to 65 kts. I think flaps were set at 10. Comments??
While I certainly do not know what happened, it seems logical that hand on reversers would be forced violently forward on deceleration from hitting ditch -- thus closing reversers.
Quote:
which eliminated that switch.
Its still there.
True -- functions slightly differently depending on serial number and ASC accomplishment. Also is pushbutton versus guarded switch on III.
Like all of you, I do not have definitive answers.
would the reverser's stow with the levers still up?
Yes, at around 60 Kts.
Believe flight manual says IF flaps greater than 22 and BOTH wheels spin up to 65 kts. I think flaps were set at 10. Comments??
While I certainly do not know what happened, it seems logical that hand on reversers would be forced violently forward on deceleration from hitting ditch -- thus closing reversers.
Quote:
which eliminated that switch.
Its still there.
True -- functions slightly differently depending on serial number and ASC accomplishment. Also is pushbutton versus guarded switch on III.
Like all of you, I do not have definitive answers.
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It would be nice if someone had a GIV systems manual, but even then, there is a lot going on here, and we may easily miss something...
Regarding conditions you site for "TR" deployment, I believe you are thinking of conditions for ground spoilers, not TR's. TR's only have to be on the ground, at idle.
Reversers will NOT stow around 60 knots, you can ride them to your parking place, and shut down both engines with them out...
Regarding nose wheel WOW circuitry, I do not believe that this WOW information is used for TR logic, since I've seen plenty of pilots deploy the TRs with the nose wheel off the ground.
Regarding conditions you site for "TR" deployment, I believe you are thinking of conditions for ground spoilers, not TR's. TR's only have to be on the ground, at idle.
Reversers will NOT stow around 60 knots, you can ride them to your parking place, and shut down both engines with them out...
Regarding nose wheel WOW circuitry, I do not believe that this WOW information is used for TR logic, since I've seen plenty of pilots deploy the TRs with the nose wheel off the ground.
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Regarding flaps 10 takeoff.
A small minority of pilots (Incorrectly) assume that you get a gentler takeoff experience for passengers with flaps 10 takeoff... The entire Gulfstream family climbs like crazy, especially on liftoff. It is not unheard of to find crews exceed flap 10 speed due to this acceleration, especially when flying with minimum fuel.
Takeoff comfort aside, flap retraction is usually accomplished beginning at 400', and you are climbing at 3,000 FPM, so it begins about 10 seconds after takeoff.... Flaps 20 to flaps 10 takes 5-8 seconds, but flaps 10 to flaps up that takes 20+ seconds.
The tradeoff* is 4-5 Kt increase in V1 speed, 500 Ft increase in takeoff length, and a minor second segment climb performance numbers.
Oh, if you want a gentle climb out for your Pax, just do a flex EPR takeoff, and pull the power back when airborne...
*ballpark estimates
A small minority of pilots (Incorrectly) assume that you get a gentler takeoff experience for passengers with flaps 10 takeoff... The entire Gulfstream family climbs like crazy, especially on liftoff. It is not unheard of to find crews exceed flap 10 speed due to this acceleration, especially when flying with minimum fuel.
Takeoff comfort aside, flap retraction is usually accomplished beginning at 400', and you are climbing at 3,000 FPM, so it begins about 10 seconds after takeoff.... Flaps 20 to flaps 10 takes 5-8 seconds, but flaps 10 to flaps up that takes 20+ seconds.
The tradeoff* is 4-5 Kt increase in V1 speed, 500 Ft increase in takeoff length, and a minor second segment climb performance numbers.
Oh, if you want a gentle climb out for your Pax, just do a flex EPR takeoff, and pull the power back when airborne...
*ballpark estimates
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"Regarding conditions you site for "TR" deployment, I believe you are thinking of conditions for ground spoilers, not TR's. TR's only have to be on the ground, at idle".
From the Flight Manual:
PROVIDING that the following conditions are met, 28V Essential DC Bus power is transmitted via the L TR CONT Circuit Breaker to the left TR arm indicator resulting in the TR ARM light on the pilot's instrument panel to illuminate:
-Left power switch (??) is in the idle position
- Left fire handle is in normal position
- T/REV EMER STOW switch is NOT depressed (and on airplanes SN 1000- 1143 excluding SN 1034 not having ASC 166 Nutcracker No. 3 relay
(on ground configuration) or on airplanes SN 1000-1143 excluding
SN 1034 having ASC 166 and airplanes SN 1034, 1144 and
subsequent.
- Either nutcracker No 3 relay energized (on ground) configuration or TR
wheel speed relay energized (wheel speed above 65 MPH (not knots)
With all the discussion about nutcracker failure or the aircraft being somehow in the air mode -- it appears we do not have enough data to intelligently speculate.
Frank R is correct. If the aircraft is in the ground mode, you can do a reverser check taxiing out -- apparently with either nutcracker #3 relay energized as long as in ground mode..
Confusion continues.
From the Flight Manual:
PROVIDING that the following conditions are met, 28V Essential DC Bus power is transmitted via the L TR CONT Circuit Breaker to the left TR arm indicator resulting in the TR ARM light on the pilot's instrument panel to illuminate:
-Left power switch (??) is in the idle position
- Left fire handle is in normal position
- T/REV EMER STOW switch is NOT depressed (and on airplanes SN 1000- 1143 excluding SN 1034 not having ASC 166 Nutcracker No. 3 relay
(on ground configuration) or on airplanes SN 1000-1143 excluding
SN 1034 having ASC 166 and airplanes SN 1034, 1144 and
subsequent.
- Either nutcracker No 3 relay energized (on ground) configuration or TR
wheel speed relay energized (wheel speed above 65 MPH (not knots)
With all the discussion about nutcracker failure or the aircraft being somehow in the air mode -- it appears we do not have enough data to intelligently speculate.
Frank R is correct. If the aircraft is in the ground mode, you can do a reverser check taxiing out -- apparently with either nutcracker #3 relay energized as long as in ground mode..
Confusion continues.
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It would be nice if someone had a GIV systems manual,
apparently with either nutcracker #3 relay energized as long as in ground mode..
On the ground with Nutcracker failed in the air mode
- Thrust reversers will stow at low speed
- Ground spoilers will deploy with wheel spin up but will stow at low speed
- Anti skid may not operate.
- All braking may be inoperative at low speed unless anti skid is selected off
- Engine idle set to 67% HP at low ground speed
IF we look at page 2A-78-00, it states
Either nutcracker #3 relay energised (On ground configuration) or TR wheel speed relay energised (wheel speed above 65 MPH)
So as you slow down and lose the wheel speed, you do not satisfy the requirements for TR deployment with the nutcracker in air mode and the TR's will stow. This is also the way that FSI are teaching the subject of landing with the nutcracker inoperative.
The T/Rs are held in the open position solely by continuous application of hydraulic pressure from the onside hydraulic system through the T/R control valves mounted in the aft equipment bay. (The "boiler room" in Gulfstream parlance) -
The combined hydraulic system supplies pressure for left T/R, and the flight system supplies the right T/R.
As I mentioned in a previous post, if the T/R's are opened during maintenance by the use of an external hydraulic cart ("mule"), and the pressure from the cart is then reduced to zero, the T/R buckets can be pushed closed by hand with a bit of effort.
The combined system supplies the landing gear actuators, so the pressure and return sides would have been breached the moment the nose gear was torn off, and even more so when the mains departed.
Both flight and combined hydraulic systems would have been further breached by the contact of the wings with the localizer antenna, as both systems supply the aileron, flight and ground spoiler actuators through multiple lines on the rear beam of both wings.
Once the airframe started coming apart, I would think that any if the normal electrical and mechanical T/R control systems would have been rendered inoperative in any case, but with the loss of hydraulics, inertia could easily have slammed the T/Rs closed, as the aircraft slid though the terrain off the end of the runway and decelerated.
Not "proven fact", but it seems the most likely explanation to me.
The combined hydraulic system supplies pressure for left T/R, and the flight system supplies the right T/R.
As I mentioned in a previous post, if the T/R's are opened during maintenance by the use of an external hydraulic cart ("mule"), and the pressure from the cart is then reduced to zero, the T/R buckets can be pushed closed by hand with a bit of effort.
The combined system supplies the landing gear actuators, so the pressure and return sides would have been breached the moment the nose gear was torn off, and even more so when the mains departed.
Both flight and combined hydraulic systems would have been further breached by the contact of the wings with the localizer antenna, as both systems supply the aileron, flight and ground spoiler actuators through multiple lines on the rear beam of both wings.
Once the airframe started coming apart, I would think that any if the normal electrical and mechanical T/R control systems would have been rendered inoperative in any case, but with the loss of hydraulics, inertia could easily have slammed the T/Rs closed, as the aircraft slid though the terrain off the end of the runway and decelerated.
Not "proven fact", but it seems the most likely explanation to me.
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OK Mutt, if the nose gear shears, will you be in air or ground mode?...
Please check your manual for me, as my memory says that while the main nutcrackers are closed circuit in ground mode, the nose nutcracker is open in ground mode....
I think that the best place to focus is why did two very experienced pilots go from VR to VR+50 knots and stay on the ground...
Please check your manual for me, as my memory says that while the main nutcrackers are closed circuit in ground mode, the nose nutcracker is open in ground mode....
I think that the best place to focus is why did two very experienced pilots go from VR to VR+50 knots and stay on the ground...
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@znightflyer
This is well understood , and i am fully aware about airports designs and runways constructions, nether the less, we have another proven example where risk mitigation would have been in favor of the people inside the plane should a system of any kind been installed. ( and not a dip like here or in Toronto with AF overrun)
By the way ; skid marks on the pavement equals antiskid to the max or no antiskid ? i.e. no hydraulics ?
It's all about $$. The FAA started requiring airports to have runway areas and if there wasn't enough room then EMAS was an option.
EMAS are great when there is not any runway safety areas (RSAs) The RSA is typically 500 feet wide and extends 1,000 feet beyond each end of the runway. Bedford meets the RSA standards. It provides a graded area in the event that an aircraft overruns, undershoots, or veers off the side of the runway. Many airports were built before the current 1,000-foot RSA standard was adopted approximately 20 years ago. They would have most likely gone through the EMAS too.
EMAS are great when there is not any runway safety areas (RSAs) The RSA is typically 500 feet wide and extends 1,000 feet beyond each end of the runway. Bedford meets the RSA standards. It provides a graded area in the event that an aircraft overruns, undershoots, or veers off the side of the runway. Many airports were built before the current 1,000-foot RSA standard was adopted approximately 20 years ago. They would have most likely gone through the EMAS too.
By the way ; skid marks on the pavement equals antiskid to the max or no antiskid ? i.e. no hydraulics ?
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crash
EMAS installed after the challenger runoff in TEB, and the southwest runoff in MDW (if im not wrong it wasnt there before).... so the EMAS folks are on the way to BED and some low politician will get credit for making BED safe.
The theory of nutcraker retraction is difficult to see because the preliminary reports indicate between 115-165kts at time of impact. so it never went down below 65kts. This was not a soft impact this was a high speed crash. Highly unlikely that trs would stow at impact, impact is impact, things dont have time to return to different positions at time of impact... This is the first thing NTSB looks at because its a tried and true system.
It sucks that the media doesnt cover this, such an important event. We just have to wait for NTSB details. With a big name like Katz I assumed that it would be nonstop coverage... but it wasn't.
I can't figure this one out, but I like reading everyones experiences and takes. Maybe flaps were not down and they tried to drop them while rolling down runway, or their trim was way off just inside t.o. trim. You can have an airplane within to trim and no horns and just a difficult time to pull aircraft off ground. Maybe they hesitated and tried to take off, aborting the abort?
The theory of nutcraker retraction is difficult to see because the preliminary reports indicate between 115-165kts at time of impact. so it never went down below 65kts. This was not a soft impact this was a high speed crash. Highly unlikely that trs would stow at impact, impact is impact, things dont have time to return to different positions at time of impact... This is the first thing NTSB looks at because its a tried and true system.
It sucks that the media doesnt cover this, such an important event. We just have to wait for NTSB details. With a big name like Katz I assumed that it would be nonstop coverage... but it wasn't.
I can't figure this one out, but I like reading everyones experiences and takes. Maybe flaps were not down and they tried to drop them while rolling down runway, or their trim was way off just inside t.o. trim. You can have an airplane within to trim and no horns and just a difficult time to pull aircraft off ground. Maybe they hesitated and tried to take off, aborting the abort?
@Fantycloud
I think you may be right with your statement that they possibly aborted the abort.
I still have a problem thinking the reverser's stowed themselves.
Just my thoughts.
I still have a problem thinking the reverser's stowed themselves.
Just my thoughts.
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Originally Posted by CL300
By the way ; skid marks on the pavement equals antiskid to the max or no antiskid ? i.e. no hydraulics ?
