Gulfstream IV in Bedford MA
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Astra driver
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If the engines are started on a legacy Gulfstream (GV models and earlier) with the control lock engaged, it cannot be disengaged without removing Hydraulic power from the controls. The correct way to do this is to shut down the engines and allow the hydraulic pressure to bleed off.
An alternative, non AFM approved method would be to pull the flight power shut off handle which would remove hydraulic power from the flight controls without having to shut down the engines and enable the gust lock to be released.
The big caveat with pulling the flight power shut off handle is that it is only guaranteed to remove hydraulic power from the controls, putting the flight power shut off handle back to its' normal position does not guarantee hydraulic power will be restored to the flight controls.
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If the engines are started on a legacy Gulfstream (GV models and earlier) with the control lock engaged, it cannot be disengaged without removing Hydraulic power from the controls. The correct way to do this is to shut down the engines and allow the hydraulic pressure to bleed off.
An alternative, non AFM approved method would be to pull the flight power shut off handle which would remove hydraulic power from the flight controls without having to shut down the engines and enable the gust lock to be released.
The big caveat with pulling the flight power shut off handle is that it is only guaranteed to remove hydraulic power from the controls, putting the flight power shut off handle back to its' normal position does not guarantee hydraulic power will be restored to the flight controls.
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I remember a scenario which played out a Chicago Midway on an airliner (think a 737). At V1/R the plane didn't rotate. Turned out the plane had been loaded improperly and the W&B trim setting was not proper. Pilot managed to get the plane into the air safely but by the skin of his teeth.
After that we were instructed to give some heft to the yoke to make sure the plane was responsive, well before V1.
This was quite awhile ago (maybe last century). And I can't remember too much about it.
I also remember an incident in which a plane made a hard landing punching the gear through the wings . Turned out another bad W&B and the plane was 20,000 lbs over the weight used to calculate Vref.
There is something about the feel of a plane that can save your life.
After that we were instructed to give some heft to the yoke to make sure the plane was responsive, well before V1.
This was quite awhile ago (maybe last century). And I can't remember too much about it.
I also remember an incident in which a plane made a hard landing punching the gear through the wings . Turned out another bad W&B and the plane was 20,000 lbs over the weight used to calculate Vref.
There is something about the feel of a plane that can save your life.
CL300,
Why is it not "guaranteed" to restore flight control power when the switch is retirned to normal? Seems hard to believe that the switch works in one direction, but might not in the opposite.
GF
Why is it not "guaranteed" to restore flight control power when the switch is retirned to normal? Seems hard to believe that the switch works in one direction, but might not in the opposite.
GF
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The Flight Power Shut Off is shown in the first diagram as a shut off valve, so one would assume that once it is reopened, normal fluid flow to the flight controls would be resumed.
We practice approach and landing with the flight power shut off ON during recurrent, all flight controls work, but just need a lot more muscle.
You may also notice that the Gust Lock isn't powered by ANY hydraulic system, it is purely mechanical.
Last edited by mutt; 3rd Jul 2014 at 17:16.
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GF,
Quote,
"Why is it not "guaranteed" to restore flight control power when the switch is retirned to normal? Seems hard to believe that the switch works in one direction, but might not in the opposite."
The flight power shut off handle is designed to be used when directed by the AFM or QRH to enable the aircraft to be flown in direct "Manual Reversion", in other words with no hydraulic boost to the controls in the event of a variety of possible flight control malfunctions. The important thing to remember here is that Gulfstream only designed it to be used in the event of an in-flight abnormality or emergency.
The handle should restore all hydraulic power when it is pushed back down, but there is no guarantee that it will do that. It is a misconception among some crews (Perhaps from repeated use in sim training) that the handle is an "On/off" switch, it was never designed as such and is only expected to be a one time use feature in real world operations.
Quote,
"Why is it not "guaranteed" to restore flight control power when the switch is retirned to normal? Seems hard to believe that the switch works in one direction, but might not in the opposite."
The flight power shut off handle is designed to be used when directed by the AFM or QRH to enable the aircraft to be flown in direct "Manual Reversion", in other words with no hydraulic boost to the controls in the event of a variety of possible flight control malfunctions. The important thing to remember here is that Gulfstream only designed it to be used in the event of an in-flight abnormality or emergency.
The handle should restore all hydraulic power when it is pushed back down, but there is no guarantee that it will do that. It is a misconception among some crews (Perhaps from repeated use in sim training) that the handle is an "On/off" switch, it was never designed as such and is only expected to be a one time use feature in real world operations.
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There seems no word has been received from the NTSB other than the first official report on June13.
The only casual word I have read about this accident was a quote from a John Goglia who apparently was with the NTSB at one time and who decided the pilot “didn’t run the checklist, so it immediately makes him a suspect for being a problem.”
This was a day or two after the accident and was not all that unusual; the “experts” always seem to start out blaming the pilot, and that is many times the only thing remembered by the general public.
I suspect that something broke, and did not become obvious until the nose didn’t come up at Vr.
I wonder if the NTSB would immediately tell the manufacturer what they have discovered just in case a problem might exist in other aircraft? Do they always wait for the Final Report to publish details of the accident?
The only casual word I have read about this accident was a quote from a John Goglia who apparently was with the NTSB at one time and who decided the pilot “didn’t run the checklist, so it immediately makes him a suspect for being a problem.”
This was a day or two after the accident and was not all that unusual; the “experts” always seem to start out blaming the pilot, and that is many times the only thing remembered by the general public.
I suspect that something broke, and did not become obvious until the nose didn’t come up at Vr.
I wonder if the NTSB would immediately tell the manufacturer what they have discovered just in case a problem might exist in other aircraft? Do they always wait for the Final Report to publish details of the accident?
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Thanks, Mutt.
I haven’t done a walkaround on this airplane.
I don’t know how easy it would be to check those springs at night in winter in Fairbanks when you’re tired, but someone in this forum mentioned in a very strong manner the “60 knot elevator free” check, and said it in a manner learned in the sim, maybe the hard way.
There was mention of some discussion of “controls” on the voice recorder. I now wonder if that was about that 60 knot check.
And I wonder if every pilot on every TO in this airplane does this 60 knot check? And is prepared to reject if the check isn’t right?
And all of this is speculation . . .
“. . . you should always follow your primary guidance (Aircraft manuals, government regulations, etc)
I haven’t done a walkaround on this airplane.
I don’t know how easy it would be to check those springs at night in winter in Fairbanks when you’re tired, but someone in this forum mentioned in a very strong manner the “60 knot elevator free” check, and said it in a manner learned in the sim, maybe the hard way.
There was mention of some discussion of “controls” on the voice recorder. I now wonder if that was about that 60 knot check.
And I wonder if every pilot on every TO in this airplane does this 60 knot check? And is prepared to reject if the check isn’t right?
And all of this is speculation . . .
“. . . you should always follow your primary guidance (Aircraft manuals, government regulations, etc)
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Gust lock to throttle interlock
Is there interlock mechanism so that when throttles are beyond 5% power the gust lock handle cannot be moved to the surfaces-locked position? (Is it impossible to engage the gust lock during the take off run?)
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Control Locks
"dogsridewith"
In normal operations it is NOT possible to engage the control locks with the engines running and producing hydraulic pressure to the flight control systems.
Your question begs a interesting thought that, would it be possible, with engines running and then pulling the "Flight Power Shutoff" handle, thereby removing hydraulic pressure from the flight controls, could it be possible to then engage the flight control lock? That question I cannot answer. Flight Power Shutoff was always taught to be used, in-flight, in the event of of a flight control malfunction(hard over or jammed; un commanded spoiler deployment).
It would be difficult to believe that a professional crew would not notice that before takeoff the flight controls were in the manual mode(not hydraulically boosted) or locked; but then again........
Thank you for your question.
MotCap
In normal operations it is NOT possible to engage the control locks with the engines running and producing hydraulic pressure to the flight control systems.
Your question begs a interesting thought that, would it be possible, with engines running and then pulling the "Flight Power Shutoff" handle, thereby removing hydraulic pressure from the flight controls, could it be possible to then engage the flight control lock? That question I cannot answer. Flight Power Shutoff was always taught to be used, in-flight, in the event of of a flight control malfunction(hard over or jammed; un commanded spoiler deployment).
It would be difficult to believe that a professional crew would not notice that before takeoff the flight controls were in the manual mode(not hydraulically boosted) or locked; but then again........
Thank you for your question.
MotCap
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My take as a long time Gulfstream driver. Reasons for a non rotatable G-IV.
Mechanically:
- Gust lock engaged and throttle pin broken. If the flight control shut off was pulled to stow the gust lock, the controls would be VERY heavy and by the time the gust lock was stowed flight control shutoff restored the airplane could have accelerated and the heavy control feel may have precipitated a high speed abort. I have been "told" that it is possible to cancel the control locks in the G-IV with both engines running without pulling the flight control shutoff because both sides of the hydraulics are at 3,000 psi. This is not so in the G-2 or 3 with both engines running because hyd pressures are 3,000 psi combined and 1,500 psi flight system.
- Trim full forward and at Vr could not be re-trimmed in the runway remaining.
- Flaps 10 instead of 20. I operated a Stage 3 G-3 which required a 10 flap TO for compliance. The VRef increased about 5 knots and TO roll about 500 ft but the second segment climb was much improved. This is about the same numbers for the G-IV and should not have been a factor except the programmed data would not match aircraft configuration so the speeds would not box (validate).
- Stall barrier failed in the "push" or stall recovery mode (has happened in the past). This condition would allow the control yoke to move from full forward to about the neutral position giving the appearance of normal elevator control. This can be overcome by depressing the disconnect button on the control yoke. This may also explain why the abort speed was so high. The pilot may have experienced a "push" and could not rotate, depressed the disconnect button and the "push" goes away. He then attempts to rotate (accelerating the whole time) releases the button for normal operation and the "push" comes back. Then attempts a high speed abort.
- Our G-IV experienced a full down auto pilot command in flight and the disconnect button did not over ride the system. A very astute pilot in the right seat (not me) looked up to his overhead CB panel and pulled the appropriate CB and the down command went away. Maintenance checked the systems and computers and found no problems. This excellent pilot informed the other crews rotating into the airplane and when the same down command happened again the next crew knew where and what CB to pull. The CB remained out until the computer was replaced. If the down command could not be cancelled, we surmise there would have been an accident. So if this scenario happened during a takeoff roll there would be no time to look and pull the CB.
- As far as adding the accelerate/go and the accelerate/stop distances, that is not how that works. Both of those distances start from start of the takeoff roll. It will take so long to apply takeoff power continue to V1 and go, as from the application of takeoff power to V1 and then stop. Not added together!
Operationally:
- The abort should have been recognized at V1 and aborted. If the abort was recognized at Vr the Accelerate/Stop would be slightly higher. Still, they should have had enough runway to stop.
- At Vr recognized a rejected TO condition, pushed a button, pulled a lever, cancelled a system that gave the impression they could continue the TO but could not then attempted to stop without adequate runway remaining.
- TRs in or out, a rejected TO, accelerate/stop distance does not include TR in the calculation. They had adequate distance with the TRs retracted.
- The flight control systems in the G-IV are mechanical, hydraulically boosted. In the case of a hard over or unmovable flight control, we then pull the flight control shutoff and go into what they call manual reversion. Very heavy controls but flyable. At no time do any of the flight controls disconnect from the yoke or rudders mechanically.
- As far as a high speed abort, the crew showed great skill staying on the centerline of the runway.
My take but I was not there so all of this is a moot point for them. My condolences to the crew and families. The only positive thing to come out of this will be the knowledge gained and future accidents to be avoided.
Mechanically:
- Gust lock engaged and throttle pin broken. If the flight control shut off was pulled to stow the gust lock, the controls would be VERY heavy and by the time the gust lock was stowed flight control shutoff restored the airplane could have accelerated and the heavy control feel may have precipitated a high speed abort. I have been "told" that it is possible to cancel the control locks in the G-IV with both engines running without pulling the flight control shutoff because both sides of the hydraulics are at 3,000 psi. This is not so in the G-2 or 3 with both engines running because hyd pressures are 3,000 psi combined and 1,500 psi flight system.
- Trim full forward and at Vr could not be re-trimmed in the runway remaining.
- Flaps 10 instead of 20. I operated a Stage 3 G-3 which required a 10 flap TO for compliance. The VRef increased about 5 knots and TO roll about 500 ft but the second segment climb was much improved. This is about the same numbers for the G-IV and should not have been a factor except the programmed data would not match aircraft configuration so the speeds would not box (validate).
- Stall barrier failed in the "push" or stall recovery mode (has happened in the past). This condition would allow the control yoke to move from full forward to about the neutral position giving the appearance of normal elevator control. This can be overcome by depressing the disconnect button on the control yoke. This may also explain why the abort speed was so high. The pilot may have experienced a "push" and could not rotate, depressed the disconnect button and the "push" goes away. He then attempts to rotate (accelerating the whole time) releases the button for normal operation and the "push" comes back. Then attempts a high speed abort.
- Our G-IV experienced a full down auto pilot command in flight and the disconnect button did not over ride the system. A very astute pilot in the right seat (not me) looked up to his overhead CB panel and pulled the appropriate CB and the down command went away. Maintenance checked the systems and computers and found no problems. This excellent pilot informed the other crews rotating into the airplane and when the same down command happened again the next crew knew where and what CB to pull. The CB remained out until the computer was replaced. If the down command could not be cancelled, we surmise there would have been an accident. So if this scenario happened during a takeoff roll there would be no time to look and pull the CB.
- As far as adding the accelerate/go and the accelerate/stop distances, that is not how that works. Both of those distances start from start of the takeoff roll. It will take so long to apply takeoff power continue to V1 and go, as from the application of takeoff power to V1 and then stop. Not added together!
Operationally:
- The abort should have been recognized at V1 and aborted. If the abort was recognized at Vr the Accelerate/Stop would be slightly higher. Still, they should have had enough runway to stop.
- At Vr recognized a rejected TO condition, pushed a button, pulled a lever, cancelled a system that gave the impression they could continue the TO but could not then attempted to stop without adequate runway remaining.
- TRs in or out, a rejected TO, accelerate/stop distance does not include TR in the calculation. They had adequate distance with the TRs retracted.
- The flight control systems in the G-IV are mechanical, hydraulically boosted. In the case of a hard over or unmovable flight control, we then pull the flight control shutoff and go into what they call manual reversion. Very heavy controls but flyable. At no time do any of the flight controls disconnect from the yoke or rudders mechanically.
- As far as a high speed abort, the crew showed great skill staying on the centerline of the runway.
My take but I was not there so all of this is a moot point for them. My condolences to the crew and families. The only positive thing to come out of this will be the knowledge gained and future accidents to be avoided.
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Takeoff Performance
A whole jet career you are trained to either abort by V1 or "go" after V1. If the aircraft doesn't rotate at Vr you still have to abort.
What the heck is the accelerate stop distance from V1 + 45 knots? Obviously more than 9,000 feet.
What the heck is the accelerate stop distance from V1 + 45 knots? Obviously more than 9,000 feet.
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inontime,
Great insights, thank you. Reading between the lines of the investigators' comments so far, I suspect that NTSB has collected enough evidence from the wreckage + flight recorders that they know exactly what happened and there will be no mystery once of the report is published (hopefully it will occur later this year).
I do wonder if a flight control check would have revealed a problem prior to the airplane entering the runway. The taxi out would have been very short, probably only a few minutes of very busy cockpit time occurred between the start of taxi and the take off roll. Although during the day Hanscom is a zoo, at 2100 on a Saturday night it would have been super quiet. They likely had a takeoff clearance well before reaching the Pine Hill hangars adjacent to taxiway Mike.
Great insights, thank you. Reading between the lines of the investigators' comments so far, I suspect that NTSB has collected enough evidence from the wreckage + flight recorders that they know exactly what happened and there will be no mystery once of the report is published (hopefully it will occur later this year).
I do wonder if a flight control check would have revealed a problem prior to the airplane entering the runway. The taxi out would have been very short, probably only a few minutes of very busy cockpit time occurred between the start of taxi and the take off roll. Although during the day Hanscom is a zoo, at 2100 on a Saturday night it would have been super quiet. They likely had a takeoff clearance well before reaching the Pine Hill hangars adjacent to taxiway Mike.
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http://www.rapp.org/archives/2012/11/gulfstream-g650-accident/
The above was an interesting read referred to in this forum about an area of aviation not many line pilots, in my experience, dwell on, or about, unless it shows up in their training.
Grumman/Gulfstream has been building outstanding airplanes for many years, not an easy task.
I’m guessing these three things would have been part of every sim check on a GIV.
“Flight crews are reminded to perform the following as set forth in the applicable AFM procedures for each model aircraft: ensure the gust lock is OFF prior to starting engines (not applicable for G650); check flight controls for freedom and correct movement prior to taxi/takeoff; [and] confirm the elevators are free during the takeoff roll,” said the letter from the manufacturer . . .
The voice recorder indicates the airplane did not rotate at VR as commanded; that caused the accident - something was broken, something did not work as it always had before.
It will be interesting to see what the Feds come up with, where they allocate blame, and what other pilots can learn from this tragedy.
The above was an interesting read referred to in this forum about an area of aviation not many line pilots, in my experience, dwell on, or about, unless it shows up in their training.
Grumman/Gulfstream has been building outstanding airplanes for many years, not an easy task.
I’m guessing these three things would have been part of every sim check on a GIV.
“Flight crews are reminded to perform the following as set forth in the applicable AFM procedures for each model aircraft: ensure the gust lock is OFF prior to starting engines (not applicable for G650); check flight controls for freedom and correct movement prior to taxi/takeoff; [and] confirm the elevators are free during the takeoff roll,” said the letter from the manufacturer . . .
The voice recorder indicates the airplane did not rotate at VR as commanded; that caused the accident - something was broken, something did not work as it always had before.
It will be interesting to see what the Feds come up with, where they allocate blame, and what other pilots can learn from this tragedy.
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The manufacturer of the jet that crashed on takeoff in Massachusetts last year, killing the co-owner of The Philadelphia Inquirer and six other people, has reported a problem with a fail-safe system that can allow the planes to reach high speeds on the runway even if they are prevented from taking off.
Gulfstream Aerospace Corp. said in a document released by the National Transportation Safety Board that the Gulfstream IV has an interlock system that is supposed to keep the plane's throttle from being moved past 6 degrees, thereby limiting acceleration, while hinged tail sections, called elevators, are immobilized.
But the company told the National Transportation Safety Board last spring that the interlock system actually allows the throttle to be moved to an average 21 degrees. The company said the issue "remained undiscovered on more than 500 aircraft over 25 years and more than 2 million takeoffs."
Still, Gulfstream contends the crash was due to the flight crew's failure to check if the gust lock system, which locks the tail sections, was engaged and to immediately abort the flight once it was clear there was a problem.
Gulfstream Aerospace Corp. said in a document released by the National Transportation Safety Board that the Gulfstream IV has an interlock system that is supposed to keep the plane's throttle from being moved past 6 degrees, thereby limiting acceleration, while hinged tail sections, called elevators, are immobilized.
But the company told the National Transportation Safety Board last spring that the interlock system actually allows the throttle to be moved to an average 21 degrees. The company said the issue "remained undiscovered on more than 500 aircraft over 25 years and more than 2 million takeoffs."
Still, Gulfstream contends the crash was due to the flight crew's failure to check if the gust lock system, which locks the tail sections, was engaged and to immediately abort the flight once it was clear there was a problem.
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NTSB Investigation of KBED Gulfstream IV Crash
Today, NTSB found the probable cause for the Gulfstream tragedy at KBED on 31 May 2014. As expected, the cause was due to the gust luck being engaged during the attempted take off and the successful application of take off thrust despite the gust lock engaged.
The NTSB video (below) reveals that the crew identified a warning associated with limited rudder control as they entered the runway, a detection of less than normal thrust allowed at the beginning of the departure roll, and an attempt to remove hydraulic power, including to the spoilers for a significant portion of the roll, while runway available passed by.
The NTSB video is quite enlightening, and there will be much more released on this accident, including the performance of the safety interlock.
I tried to put this post on the original 2014 thread, but could not find it on the mobile site.
youtube.com/watch?v=GokKYNOcp20&t=127
The NTSB video (below) reveals that the crew identified a warning associated with limited rudder control as they entered the runway, a detection of less than normal thrust allowed at the beginning of the departure roll, and an attempt to remove hydraulic power, including to the spoilers for a significant portion of the roll, while runway available passed by.
The NTSB video is quite enlightening, and there will be much more released on this accident, including the performance of the safety interlock.
I tried to put this post on the original 2014 thread, but could not find it on the mobile site.
youtube.com/watch?v=GokKYNOcp20&t=127
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The Phila. Enquirer reported today that part of the Safety Board findings was that the pilots did not perform all their pre-flight checks 98% of the time during the past several years. So IMO it was almost inevitable that something like this would occur. Being a non-pilot, I was amazed at that fact; I could understand sometimes being in a rush and not doing what you are supposed to do, but 98% of the time? Amazing is all I can say.
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There was a story written on this accident recently. I found some of the comments interesting and will post them here. Some have been edited to remove extraneous info. They may or may not be correct.
"My understanding is that the gust lock/FPSOV engages a hydraulic cut-off valve to the primary flight controls, and/or a thrust interlock preventing max thrust. The safety analysis for that system must be a darn good read, as those are both catastrophic failure items.
Not entirely the pilots fault - some complacency contributed for sure, but the gust lock system sounds flawed.
Knowing that, if I was a G450 pilot I would be doing a full-and-free exterior flight control check pre-takeoff everytime, and where-ever possible I would simply never engage the gust lock - pay extra to have the aircraft hangared!
From 7700 dot com;
1.Check the two gust lock springs below the elevator assembly in the aft equipment compartment during every exterior preflight inspection. (Some crews do not preflight the aft equipment compartment at all; this is not smart.)
2.Ensure the gust lock is off prior to engine start. (This is in the manual and tends to be self-correcting: the throttles will not move unless the throttle lock is broken.)
3.Accomplish a complete flight control check after every engine start. (Some crews skip this routinely; this is not smart.)
4.Accomplish an elevator free check at 60 knots during takeoff. (Some crews skip this or have invented alternate procedures which could actually make things worse. Not smart!)
5.Engage the gust lock when leaving the aircraft without hydraulic power and test each axis and the throttles to ensure it is working.
There is an undocumented technique among undisciplined GIV pilots to use the FPSOV to remove hydraulic power from the flight controls after engine start in case they forgot to disengage the gust lock. I've never seen this done but am assured it works. This technique is not correct and could damage the airplane. The correct procedure would be to shut down the engines, disengage the gust lock, and restart the engines. Whether it works in the chocks after engine start or not, it cannot work with any kind of air loads on the elevator. If the relative wind is pushing up on the elevator, the gust lock hook will have pressure loads that the gust lock handle cannot overcome.
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There is nothing wrong with the Gust Lock System on a Gulfstream. The Gulfstream GIV uses the same Gust Lock System that is installed in the GII and GIII. There is a BIG RED Handle that is pulled up, it is approx 10" long with the words Gust Lock in white on the handle right next to the Throttles. The Flight Power Shut Off Valve (FPSOV) is not associated with the Gust Lock at all. The foolish crew, instead of aborting while they had time/runway, decided to force the takeoff by unloading the Hydraulic System in "hopes" that it would allow the Gust Lock to be disengaged.
What the NTSB doesn't discuss, or at least put much emphasis is that the same flight crew set the gust lock. The fix for this is really easy . . . FOLLOW the Checklist . . . and perform a flight control check in the chocks.
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I used to fly GIV-SP's and G450's in South America, a few years ago. Among the most significant airplanes I flew along my whole career (i.e. B737's, Airbus A310 / A300-600, Fokker 100, Learjet 60 etc), Gulfstreams were by far the most impressive, by all means. A very challenging and high-workload routine, though, with all those functional checks. On the first flight of the day - for the sake of expediting the departure as the big boss arrived (most of the times late), as well as not missing the ATC slots -, we used to break the cockpit preparation in two or three phases, but always quickly-reviewing the previous one(s) while performing the next, in order not to affect operational safety. It is a complex corporate airplane, full of "bad-a** triggers" and demands extra attention, in many senses.
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Ask any Gulfstream pilot what the weak point on the aircraft is and they will tell you it is the gust lock. Once you start the engines you can't disengage the gust lock without shutting down.
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One issue is that the manufacturer's normal checklists include too many items that are really maintence checks or should be performed only on the first flight of the day. The manufacturer includes all those checks not for operational considerations of safety but to protect them, the manufacturer, from liability should an accident occur. There's no reason why a before start checklist should have so many items that it takes an experienced crew thirty minutes to start the engines and possibly another twenty minutes to get to the hold short line. This is what leads flight crews to start shortening the checklists because they see no reason to perform those checks on every leg. Once you begin to omit checks it's easy to skip an important one such as the flight controls.
I've operated and maintained Gulfstream's for over 30 years: GII, GIII, GIV, G450, G550. The gustlock system on the GIV provides a throttle interlock, which restricts throttle movement. Here are the facts: the pilots had a rudder limit message on the EICAS before takeoff. They discussed this, during taxi. That alone should have been reason to stop and investigate.
They started the takeoff roll, engaged autothrottles, but clearly did not observe that the engines were not making take off power, and then realizing the gustlock was engaged, tried to disarm the gustlock while rolling, rather than shut down power and do it. By then, the airload on the elevators provided enough force on the gustlock mechanism that it would not release.
So, is it the aircraft/manufacturer's fault? I think not. The crew had multiple warnings facing them, yet blindly continued.
The one thing the manufacturer is on the hook for: the gustlock system was never actually operationally certified, according to the NTSB report. Because it had been used on past models, it was certified by way of drawing And design review. This factor lead to the amount of power you could achieve with the gustlock engaged on the GIV being inconsistent across the fleet, and several GIV's tested post accident showed that more power than specified could be achieved on some aircraft.
It's important to note however, that the crash aircraft did not achieve anywhere near takeoff power. I suspect that the aircraft, being very light for the takeoff and short trip, also contributed to masking the fact that acceleration was less than should be expected. Again though, an experienced crew should have picked up on this.
You cannot blame anyone but the crew in this case however: the chain of events that lead up to the crash was glaring. Particularly at the point where they realized the gust lock was on, and still continued the takeoff!
"My understanding is that the gust lock/FPSOV engages a hydraulic cut-off valve to the primary flight controls, and/or a thrust interlock preventing max thrust. The safety analysis for that system must be a darn good read, as those are both catastrophic failure items.
Not entirely the pilots fault - some complacency contributed for sure, but the gust lock system sounds flawed.
Knowing that, if I was a G450 pilot I would be doing a full-and-free exterior flight control check pre-takeoff everytime, and where-ever possible I would simply never engage the gust lock - pay extra to have the aircraft hangared!
From 7700 dot com;
1.Check the two gust lock springs below the elevator assembly in the aft equipment compartment during every exterior preflight inspection. (Some crews do not preflight the aft equipment compartment at all; this is not smart.)
2.Ensure the gust lock is off prior to engine start. (This is in the manual and tends to be self-correcting: the throttles will not move unless the throttle lock is broken.)
3.Accomplish a complete flight control check after every engine start. (Some crews skip this routinely; this is not smart.)
4.Accomplish an elevator free check at 60 knots during takeoff. (Some crews skip this or have invented alternate procedures which could actually make things worse. Not smart!)
5.Engage the gust lock when leaving the aircraft without hydraulic power and test each axis and the throttles to ensure it is working.
There is an undocumented technique among undisciplined GIV pilots to use the FPSOV to remove hydraulic power from the flight controls after engine start in case they forgot to disengage the gust lock. I've never seen this done but am assured it works. This technique is not correct and could damage the airplane. The correct procedure would be to shut down the engines, disengage the gust lock, and restart the engines. Whether it works in the chocks after engine start or not, it cannot work with any kind of air loads on the elevator. If the relative wind is pushing up on the elevator, the gust lock hook will have pressure loads that the gust lock handle cannot overcome.
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There is nothing wrong with the Gust Lock System on a Gulfstream. The Gulfstream GIV uses the same Gust Lock System that is installed in the GII and GIII. There is a BIG RED Handle that is pulled up, it is approx 10" long with the words Gust Lock in white on the handle right next to the Throttles. The Flight Power Shut Off Valve (FPSOV) is not associated with the Gust Lock at all. The foolish crew, instead of aborting while they had time/runway, decided to force the takeoff by unloading the Hydraulic System in "hopes" that it would allow the Gust Lock to be disengaged.
What the NTSB doesn't discuss, or at least put much emphasis is that the same flight crew set the gust lock. The fix for this is really easy . . . FOLLOW the Checklist . . . and perform a flight control check in the chocks.
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I used to fly GIV-SP's and G450's in South America, a few years ago. Among the most significant airplanes I flew along my whole career (i.e. B737's, Airbus A310 / A300-600, Fokker 100, Learjet 60 etc), Gulfstreams were by far the most impressive, by all means. A very challenging and high-workload routine, though, with all those functional checks. On the first flight of the day - for the sake of expediting the departure as the big boss arrived (most of the times late), as well as not missing the ATC slots -, we used to break the cockpit preparation in two or three phases, but always quickly-reviewing the previous one(s) while performing the next, in order not to affect operational safety. It is a complex corporate airplane, full of "bad-a** triggers" and demands extra attention, in many senses.
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Ask any Gulfstream pilot what the weak point on the aircraft is and they will tell you it is the gust lock. Once you start the engines you can't disengage the gust lock without shutting down.
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One issue is that the manufacturer's normal checklists include too many items that are really maintence checks or should be performed only on the first flight of the day. The manufacturer includes all those checks not for operational considerations of safety but to protect them, the manufacturer, from liability should an accident occur. There's no reason why a before start checklist should have so many items that it takes an experienced crew thirty minutes to start the engines and possibly another twenty minutes to get to the hold short line. This is what leads flight crews to start shortening the checklists because they see no reason to perform those checks on every leg. Once you begin to omit checks it's easy to skip an important one such as the flight controls.
I've operated and maintained Gulfstream's for over 30 years: GII, GIII, GIV, G450, G550. The gustlock system on the GIV provides a throttle interlock, which restricts throttle movement. Here are the facts: the pilots had a rudder limit message on the EICAS before takeoff. They discussed this, during taxi. That alone should have been reason to stop and investigate.
They started the takeoff roll, engaged autothrottles, but clearly did not observe that the engines were not making take off power, and then realizing the gustlock was engaged, tried to disarm the gustlock while rolling, rather than shut down power and do it. By then, the airload on the elevators provided enough force on the gustlock mechanism that it would not release.
So, is it the aircraft/manufacturer's fault? I think not. The crew had multiple warnings facing them, yet blindly continued.
The one thing the manufacturer is on the hook for: the gustlock system was never actually operationally certified, according to the NTSB report. Because it had been used on past models, it was certified by way of drawing And design review. This factor lead to the amount of power you could achieve with the gustlock engaged on the GIV being inconsistent across the fleet, and several GIV's tested post accident showed that more power than specified could be achieved on some aircraft.
It's important to note however, that the crash aircraft did not achieve anywhere near takeoff power. I suspect that the aircraft, being very light for the takeoff and short trip, also contributed to masking the fact that acceleration was less than should be expected. Again though, an experienced crew should have picked up on this.
You cannot blame anyone but the crew in this case however: the chain of events that lead up to the crash was glaring. Particularly at the point where they realized the gust lock was on, and still continued the takeoff!