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Gulfstream IV in Bedford MA

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Gulfstream IV in Bedford MA

Old 13th Jun 2014, 19:47
  #141 (permalink)  
 
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Mutt,
Quote, "I thought that the elevator stayed in the same slightly down position if the lock was engaged or not engaged, the lock just stopped it moving with the wind."

On the legacy Gulfstream models, G550 and earlier, the control column will fall full forward (nose down) when the control lock is released and the controls are not air loaded.

(On the G650, which is FBW, the control column stays in the upright, neutral position at all times unless it is moved. As a side note, there is no control lock on the G650.)
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Old 13th Jun 2014, 20:00
  #142 (permalink)  
 
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Gulfstream just distributed this "MOL"

TO:
SUBJECT:
MAINTENANCE AND OPERATIONS LETTER
June 13, 2014 ALL-MOL-14-0015
FLIGHT CREW OPERATIONAL INFORMATION
All Gulfstream Operators
General (ATA 00) Airplane Flight Manual (AFM) Procedures
Gulfstream is issuing this Maintenance and Operations Letter (MOL) to remind flight crews of the
importance of adhering to flight procedures published in applicable Airplane Flight Manuals (AFM) to confirm flight control integrity and freedom of motion. 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
 Confirm the elevators are free during the takeoff roll
If you have questions or comments regarding this communication, please contact Customer Support at 800-810-GULF (4853) or 912-965-4178, by fax at 912-965-4184, or by electronic mail at [email protected].
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Old 13th Jun 2014, 20:30
  #143 (permalink)  
 
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I wonder if the FDR or CVR recorded the after start control check?
CVR (verbal) info does not mean sht if investigating actual actions.....
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Old 13th Jun 2014, 20:52
  #144 (permalink)  
 
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I guess the key word is "consistent" in this report. It begs the question on how they were able to set T/O thrust if the gust lock was engaged.

"The FDR data revealed the elevator control surface position during the taxi and takeoff was consistent with its position if the gust lock was engaged."

"The airplane was equipped with a mechanical gust lock system, which could be utilized to lock the ailerons and rudder in the neutral position, and the elevator in the down position to protect the control surfaces from wind gusts while parked. A mechanical interlock was incorporated in the gust lock handle mechanism to restrict the movement of the throttle levers to a minimal amount (6-percent)"

Last edited by tlbrown350; 13th Jun 2014 at 21:07.
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Old 14th Jun 2014, 06:02
  #145 (permalink)  
 
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"A mechanical interlock was incorporated in the gust lock handle mechanism to restrict the movement of the throttle levers to a minimal amount (6-percent)"


So was the throttle restrictive feature of the gust lock mechanism designed with failsafe feature(s)? (Sounds like it was.)
Were there any write-ups on the gust lock operation?
Why was this system design deleted in later model aircraft?
Has anyone on this forum flown this model aircraft?
I understand the visible handle of the gust lock was observed to be in the OFF position, and that portion of the cockpit appears intact.
It's my understanding that if the gust lock feature was engaged he couldn't have advanced the throttle for TO.
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Old 14th Jun 2014, 07:53
  #146 (permalink)  
 
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??

Cant find the link to that document .....
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Old 14th Jun 2014, 11:13
  #147 (permalink)  
 
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Can somebody please explain how the elevator "correct sense" check is carried out on this type of aircraft?
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Old 14th Jun 2014, 12:57
  #148 (permalink)  
 
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Originally Posted by Hadley Rille View Post
Can somebody please explain how the elevator "correct sense" check is carried out on this type of aircraft?
There really is no "correct sense" check that can be done by the flight crew, insofar as determining from the flight deck that the elevator moves on the correct direction - i.e. up with aft yoke movement, and down with forward yoke movement. Unlike later models like the G-550, the G-IV has no control surface position displays on the flight deck for ailerons, elevators or spoilers.

The only check that the crew can do is to insure that the flight controls have full freedom of movement before flight. Based on the NTSB preliminary report, the FDR data does not indicate that this was accomplished prior to commencing takeoff - potentially a key omission.

Obviously the pitch control system was working on the aircraft's inbound flight to BED from ACY, so whatever failure occurred to prevent rotation, happened at some point between landing and the next (unsuccessful) attempt to take off.
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Old 14th Jun 2014, 14:00
  #149 (permalink)  
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I understand the visible handle of the gust lock was observed to be in the OFF position, and that portion of the cockpit appears intact.
It's my understanding that if the gust lock feature was engaged he couldn't have advanced the throttle for TO
That is what baffled me at first until this clue.
On the legacy Gulfstream models, G550 and earlier, the control column will fall full forward (nose down) when the control lock is released and the controls are not air loaded.
The actual locking device is armed to engage or disengage with the lever along with the throttle block.
However, in some form or fashion mechanically or hydraulically the elevator mechanism has to be separated from the yoke and commanded down for the lock to engage.
So obviously the falling forward of the yoke realigns the yoke or doing control checks accomplish the same result of resetting the yoke to the elevator commands.


If the pilots were holding neutral position of the yoke, released the gust lock on taxi and then the lock itself would disengage, BUT did not do control check then the yoke would not reset itself to align with the elevator control commands.


So by falling out of normal start sequence they missed both opportunities to realign/reset the elevator functions.
That is my limited interpretation anyway.
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Old 14th Jun 2014, 14:42
  #150 (permalink)  
 
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Thanks for the reply JRB. It's odd that a check that's so simple in a SEP is effectively not done in a more sophisticated aircraft (without position displays).
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Old 14th Jun 2014, 18:48
  #151 (permalink)  
 
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“If the pilots were holding neutral position of the yoke, released the gust lock on taxi and then the lock itself would disengage, BUT did not do control check then the yoke would not reset itself to align with the elevator control commands.”

“The report also indicated a possible problem with a mechanical gust lock system, which protects aircraft components from wind damage while planes are parked. Aviation experts say the plane would have been unable to take off if the lock was engaged.”

As I understand this situation, you might set the gust lock to protect the parked airplane before you leave because it will be sitting for a while.
Then you get a call on the cellphone alerting you that the passengers are on the way to the airport. One thing you visually check in the cockpit is that the gust control lever is OFF either before or during the reading of the checklist. The Captain was also a mechanic so he would probably see things that the average pilot, like me, might miss. A friend of mine was Maintenance Officer at a USAF ADC base in MA back in the fifties and he used to take a random mechanic off the flight line on test hops of one of his F89’s, a move calculated to help avoid another reverse control hookup he had experienced.

Question: Placing the gust control lever in the OFF position in this Gulfstream does not actually turn the gust control OFF until - and unless - you do a control check?

I would think that placing the Gust Control Lever to the OFF position would turn the Gust Control OFF.

Gulfstream builds a nice airplane – why the extra step to turn the Gust Control OFF? You will have your hands on the controls as you start the TO roll and that feel will tell you if things are normal whether or not you actually did a full control check. The B767 was the last plane I flew and its controls were pretty simulator-like numb but you would know early on if they were not right. The Gulfstream is very light by comparison and would have a very lively feel I would think.

Admittedly I am out of the loop age-wise but I recall, for instance, a young USAF pilot flying strip alert take off with his seat belt inadvertently unfastened. Checklists are handy but do not cover all categories, especially if you are in a hurry, or hurried.

I am curious because apart from the tragedy of the deaths of those on this airplane, I was startled to read recently that Gulfstream lost a brand new airplane with their own test pilots on a test hop. I do not know what caused this accident but if that particular Gulfstream crew, or engineering staff, missed something, there may be something more than the infamous pilot error afoot here.

Each death is an individual heartrending tragedy to all, and the particular loss of Lewis Katz is a big loss to the community as well. He helped a lot of people.

Aircraft accidents are the biggest learning curve we surf in this industry, and as Ernie Gann pointed out, Fate is out there looking for each of us. That you have never scratched an airplane does not mean that you won’t, or can’t.
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Old 14th Jun 2014, 18:59
  #152 (permalink)  
 
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Originally Posted by VFD View Post
That is what baffled me at first until this clue. The actual locking device is armed to engage or disengage with the lever along with the throttle block. However, in some form or fashion mechanically or hydraulically the elevator mechanism has to be separated from the yoke and commanded down for the lock to engage. So obviously the falling forward of the yoke realigns the yoke or doing control checks accomplish the same result of resetting the yoke to the elevator commands. If the pilots were holding neutral position of the yoke, released the gust lock on taxi and then the lock itself would disengage, BUT did not do control check then the yoke would not reset itself to align with the elevator control commands. So by falling out of normal start sequence they missed both opportunities to realign/reset the elevator functions. That is my limited interpretation anyway. VFD
It's not quite as complicated as that, there is no mechanical or hydraulic "separation" of the yoke from the elevator. Pulling the control lock lever upward merely causes a latching pin to slide into a matching hole in one of the bellcranks which are part of the normal elevator mechanical control interconnection from the flight deck to the aft equipment bay. Pushing the control lock lever down causes the latching pin to retract. The latching pins for elevator, ailerons and rudder are all controlled by cables which have a common connection at the lock lever.

The elevator's natural position on the ground with no hydraulic power applied is fully down, which corresponds to the yoke being fully forward. The position where the locking latch will engage is very close to the full down position. When engaging the lock, the pilot might have to pull the yoke back an inch or two until the lock lever will come fully up, but it is not a significant distance.

The preliminary report indicates that the locking latch for the elevator was found disengaged, and though it could have retracted from the impact forces of the crash, I would think that if it HAD been engaged at impact, there would have been some mechanical damage to the latch, or it's mounting bracket - apparently there was no indication of that.

From a psychological perspective, I would think that if the yoke was locked, or mechanically jammed in such a way that the yoke could not be pulled back - that the pilot's instinctive reaction would have been to instantly recognize that a serious problem existed, and to have initiated an abort immediately.

Instead, all indications are that the abort was only initiated many seconds after VR, which seems to point to the possibility that the yoke came back normally, and the problem was not recognized until the nose failed to rise as would be expected in a typical rotation, consuming many precious seconds, and many hundreds of feet of remaining runway.

If so, this would point to a failure in the mechanical control path between yoke and elevator in which the elevator did not respond to movement of the yoke.... but in such a way that the yoke travel was not restricted. A broken control cable would be my first thought - but there are other possibilities.
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Old 14th Jun 2014, 20:09
  #153 (permalink)  
 
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see post 38.
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Old 15th Jun 2014, 15:32
  #154 (permalink)  
 
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I was thinking cable problem, but not the yolk to elevator cable, rather, the cable the actuates the pin on the elevator lock. If this cable were damaged and/or mis-adjusted, the locking pin may have pulled out part way thus temporarily freeing the elevator mechanism, but after the take-off roll commenced, the vibration, movement, ect., may have caused the pin to re-engage the lock hole thus freezing the elevator. I'm not familiar with the gust lock mechanism on the GIV so I don't know exactly what the failure modes are, so this is a bit of speculation on my part.
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Old 15th Jun 2014, 18:47
  #155 (permalink)  

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Instead, all indications are that the abort was only initiated many seconds after VR, which seems to point to the possibility that the yoke came back normally, and the problem was not recognized until the nose failed to rise as would be expected in a typical rotation, consuming many precious seconds, and many hundreds of feet of remaining runway.
My thinking is trending to go in that direction. Based on an incident that happened to me back in 1981 when the aircraft I was flying failed to rotate at V-R. There is a WTF pause at that moment, that costs some time, precious time I might add.

In my case I was able to finally rotate with full up elevator while applying up trim. There was not enough runway left to consider an abort. The cause was a forward CG issue that I was not made aware of.
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Old 15th Jun 2014, 19:33
  #156 (permalink)  
 
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From the report -
"The flap handle in the cockpit was observed in the 10 degree detent. FDR data indicated a flap setting of 20 degrees during the takeoff attempt."

The disagreement between the flap handle position (10) and the flap setting during takeoff (20) is interesting. Does Gulfstream specify a flap setting prior to an evacuation ?
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Old 15th Jun 2014, 23:43
  #157 (permalink)  
 
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If no maintenance was carried out during the stop, the normal control check for freedom of movement could be safely assumed to also be a check for correct movement.

It's interesting that the initial report says that there was no evidence of a control check prior to takeoff. That would mean that if there was some restriction to free movement of the elevator, that would only have become apparent at some time during the takeoff.

That said, though, I doubt that the control column should remain fully or almost fully forward during the takeoff roll, where it would be with the aircraft stationary with the controls locked. You would expect it to sort of "float" backwards to a neutral position in response to air loads, the column position corresponding to the elevator position, ready for the nose-up input associated with the "Rotate" call at VR. Not seeing the column move in that way should have triggered some sort of response from the crew, so that a working assumption would be that the control column did move aft in the normal way. This logic I am using argues that the controls were not locked.

This is still a puzzling accident, so that it will be very interesting to read the final report, but reading that there's no evidence of a control check seems to be one piece falling into place.
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Old 16th Jun 2014, 02:51
  #158 (permalink)  
 
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JPJP
Do you think that if the flight crew escaped uninjured after the crash that they would be concerned about flap position for an emergency exit ?????
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Old 16th Jun 2014, 03:29
  #159 (permalink)  
 
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Originally Posted by JPJP View Post
From the report - "The flap handle in the cockpit was observed in the 10 degree detent. FDR data indicated a flap setting of 20 degrees during the takeoff attempt." The disagreement between the flap handle position (10) and the flap setting during takeoff (20) is interesting. Does Gulfstream specify a flap setting prior to an evacuation ?
Although the cockpit section of the airframe appeared relatively intact in the post-crash photos, hard to say how much structural damage occurred inside, or how severe the deceleration forces were. The flap handle has a latch that locks it into place at each detent, but quite possible I suppose, that it could have been driven forward from 20 to 10 degrees in the crash - especially if it was hit by something from behind, or if the linkage below the flap handle broke off.

Would explain the initial mystery of why the crew seemingly chose to do a Flaps 10 takeoff, when conditions didn't really call for it. If the FDR record is accurate, it was a standard Flaps 20 departure after all.
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Old 16th Jun 2014, 03:57
  #160 (permalink)  
 
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Originally Posted by areobat View Post
I was thinking cable problem, but not the yolk to elevator cable, rather, the cable the actuates the pin on the elevator lock. If this cable were damaged and/or mis-adjusted, the locking pin may have pulled out part way thus temporarily freeing the elevator mechanism, but after the take-off roll commenced, the vibration, movement, ect., may have caused the pin to re-engage the lock hole thus freezing the elevator. I'm not familiar with the gust lock mechanism on the GIV so I don't know exactly what the failure modes are, so this is a bit of speculation on my part.
That possibility has crossed my mind. However, during my initial maintenance training on the G-IV many years ago, we were told that the hydraulic actuators are capable of producing more than enough force to shear the lock latches right off of their mounting brackets if the associated flight controls are moved forcefully in the cockpit. One reason why the checklist calls for the control lock lever to be released before engine start.

I don't know about the aileron and elevator locks, but there have apparently been several incidents in the G-IVs history of flight crews breaking the rudder control lock by pressing a rudder pedal after engine start with the lock lever still engaged.

Though, that probably would be easy to do, as the rudder has the largest and most powerful hydraulic actuator in the entire flight control system.
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