Gulfstream IV in Bedford MA
The hydraulics lines were compromised at the loss of the NLG after the aircraft left the runway.
There would be no braking other than the Emergency Park Brake.
With a total fluid loss and no pressure to hold them open the TRs would be forced from the deployed position to the stowed position by the engine thrust on the deflectors.
There would be no braking other than the Emergency Park Brake.
With a total fluid loss and no pressure to hold them open the TRs would be forced from the deployed position to the stowed position by the engine thrust on the deflectors.
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Well, yes, but that's so late in the crash sequence, the loss of hydraulics, just after the aircraft has left the runway at something like 100 knots, that this will have made very little difference to the accident outcome. You can not get very good braking action off an unpaved surface, for one thing.
I think the focus will be on why the aircraft did not rotate at VR. What happened after that seems fairly obvious, finding out that you have an aircraft you can not make fly at 165 knots.
I think the focus will be on why the aircraft did not rotate at VR. What happened after that seems fairly obvious, finding out that you have an aircraft you can not make fly at 165 knots.
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I do not believe that they lost braking. The picture a few posts ago shows plenty of brake action. And the Combined hydraulic reservoir is large, around five and a half gallons if memory serves, and the engine pumps can easily overcome the escaping loss and provide pressure until the reservoir runs dry. The 550 has "fuses" that shut off fluid to the nose should this occur, but I don't know about the IV. If they had been using the emergency/parking brake, they would not have had anti-skid...
It took around 25 seconds to accelerate to V1 (around 115K), and the CVR ended at 49 seconds. They accelerated to 165 Knots yet didn't fly.... Understanding this tragic accident isn't a systems question, it's a "why" question.
It took around 25 seconds to accelerate to V1 (around 115K), and the CVR ended at 49 seconds. They accelerated to 165 Knots yet didn't fly.... Understanding this tragic accident isn't a systems question, it's a "why" question.
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One thing that has been puzzling me is why there was a such a substantial over run at such a high speed, like many others I would think that there had to have been some other conspiring factor to cause such a large over run.
Out of curiosity I used the performance manuals for the G3 and G5 (No longer have any G4 manuals lying around) and came up with some rough numbers for stopping distances at approach speeds of 165 knots, these were typically in the region of 7,800 ft, at 500ft field elevation, unfactored, no wind. Subtract 1,000 ft from this to account for the 50ft threshold crossing height distance and an additional 1,400 ft credit for both thrust reversers operating and you get an approximate stopping distance on hard surface of 5,400ft.
Add to this the distance required to accelerate to 165 knots which I estimate to be at least 4,400ft (BFL's for flaps 10, field elevation 500ft, GTOW 60,000lb, come out to around this number)
Add these two numbers together, 4,400ft to go and 5,400 to stop and you get 9,800ft total.
Total distance from the start of the runway to the gully is approximately 8,900ft
(7,011 ft + 1,000ft overrun + ~890 ft to the gully)
Not saying that there weren't any other failures during the abort, just that a considerable overrun was a certainty with an abort started that far past V1 even with everything working perfectly.
Out of curiosity I used the performance manuals for the G3 and G5 (No longer have any G4 manuals lying around) and came up with some rough numbers for stopping distances at approach speeds of 165 knots, these were typically in the region of 7,800 ft, at 500ft field elevation, unfactored, no wind. Subtract 1,000 ft from this to account for the 50ft threshold crossing height distance and an additional 1,400 ft credit for both thrust reversers operating and you get an approximate stopping distance on hard surface of 5,400ft.
Add to this the distance required to accelerate to 165 knots which I estimate to be at least 4,400ft (BFL's for flaps 10, field elevation 500ft, GTOW 60,000lb, come out to around this number)
Add these two numbers together, 4,400ft to go and 5,400 to stop and you get 9,800ft total.
Total distance from the start of the runway to the gully is approximately 8,900ft
(7,011 ft + 1,000ft overrun + ~890 ft to the gully)
Not saying that there weren't any other failures during the abort, just that a considerable overrun was a certainty with an abort started that far past V1 even with everything working perfectly.
Last edited by Astra driver; 11th Jun 2014 at 04:00.
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One of our aircraft (accidents) is (seemingly) missing.
N T S B - Aviation Accidents - Index of Months
N T S B - Aviation Accidents - Index of Months
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I don't know the airplane, but are the gust locks physically outside and need to be removed?
http://www.smartcockpit.com/aircraft..._Controls.html
The Gulfstream IV primary flight controls system, shown in Figure 1, is a mechanically
actuated, hydraulically operated system that provides boosted surface control to
overcome the aerodynamic forces associated with high speed flight. This allows the
aircraft to be comfortably and reliably steered through the pitch, roll and yaw axes.
The primary flight control surfaces (elevators, ailerons and rudder) are positioned by
tandem type hydraulic actuators. The actuators receive hydraulic operating pressure
from both the Combined and Flight hydraulic systems, as shown in Figure 2. Both
hydraulic systems maintain a system pressure of 3000 psi. Loss of a single hydraulic
system has no effect on operation of the primary flight controls, as the remaining system
is capable of maintaining actuator load capacity. In the event of total loss of hydraulic
pressure in both hydraulic systems, the primary flight controls revert to manual operation.
Mechanical pitch, roll and yaw trim systems allow the flight crew to trim the aircraft. The
pitch trim system can also be controlled electrically by pitch trim switches on the control
wheels.
A gust lock secures the elevators, ailerons and rudder to prevent wind gust damage to
the surfaces.
Secondary flight controls, shown in Figure 1, include flaps, ground spoilers and
speedbrakes. These flight controls are hydraulically powered and electrically or
mechanically controlled. The mechanically operated horizontal stabilizer moves in
conjunction with the flaps to maintain longitudinal trim.
An Angle-of-Attack (AOA) system provides outputs to the control column shakers, control
column pusher, approach indexers, normalized AOA display and stall barrier system. The
control column shakers provides early warning of a stall scenario by vibrating the control
column before the stall while the control column pusher automatically initiates lowering
the nose if the stall is imminent.
The Gulfstream IV uses an aircraft configuration warning system to monitor landing gear,
flap, speed brake and power lever position. If an unsafe configuration is detected, the
system provides a visual and / or aural warning.
On CAA certified aircraft, a flight control automatic failure detection system compares
control inputs to actuator outputs. If a malfunction is detected, the system shuts off power
to the affected actuator.
The flight controls system is divided into the following subsystems:
• 2A-27-20: Pitch Flight Control System
• 2A-27-30: Yaw Flight Control System
• 2A-27-40: Roll Flight Control System
• 2A-27-50: Horizontal Stabilizer System
• 2A-27-60: Flaps System
• 2A-27-70: Spoiler System
• 2A-27-80: Gust Lock System
http://www.smartcockpit.com/aircraft..._Controls.html
The Gulfstream IV primary flight controls system, shown in Figure 1, is a mechanically
actuated, hydraulically operated system that provides boosted surface control to
overcome the aerodynamic forces associated with high speed flight. This allows the
aircraft to be comfortably and reliably steered through the pitch, roll and yaw axes.
The primary flight control surfaces (elevators, ailerons and rudder) are positioned by
tandem type hydraulic actuators. The actuators receive hydraulic operating pressure
from both the Combined and Flight hydraulic systems, as shown in Figure 2. Both
hydraulic systems maintain a system pressure of 3000 psi. Loss of a single hydraulic
system has no effect on operation of the primary flight controls, as the remaining system
is capable of maintaining actuator load capacity. In the event of total loss of hydraulic
pressure in both hydraulic systems, the primary flight controls revert to manual operation.
Mechanical pitch, roll and yaw trim systems allow the flight crew to trim the aircraft. The
pitch trim system can also be controlled electrically by pitch trim switches on the control
wheels.
A gust lock secures the elevators, ailerons and rudder to prevent wind gust damage to
the surfaces.
Secondary flight controls, shown in Figure 1, include flaps, ground spoilers and
speedbrakes. These flight controls are hydraulically powered and electrically or
mechanically controlled. The mechanically operated horizontal stabilizer moves in
conjunction with the flaps to maintain longitudinal trim.
An Angle-of-Attack (AOA) system provides outputs to the control column shakers, control
column pusher, approach indexers, normalized AOA display and stall barrier system. The
control column shakers provides early warning of a stall scenario by vibrating the control
column before the stall while the control column pusher automatically initiates lowering
the nose if the stall is imminent.
The Gulfstream IV uses an aircraft configuration warning system to monitor landing gear,
flap, speed brake and power lever position. If an unsafe configuration is detected, the
system provides a visual and / or aural warning.
On CAA certified aircraft, a flight control automatic failure detection system compares
control inputs to actuator outputs. If a malfunction is detected, the system shuts off power
to the affected actuator.
The flight controls system is divided into the following subsystems:
• 2A-27-20: Pitch Flight Control System
• 2A-27-30: Yaw Flight Control System
• 2A-27-40: Roll Flight Control System
• 2A-27-50: Horizontal Stabilizer System
• 2A-27-60: Flaps System
• 2A-27-70: Spoiler System
• 2A-27-80: Gust Lock System
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The airplane could not rotate. The G-IV does not have HOPS or a way to disconnect/separate the elevator in the event of a jam. There is only one elevator actuator which is hydraulically powered by both (L/R) systems. All the ink about aborts and WOW switches seem to miss the point IMHO.
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Has runaway stab trim nose down on TO roll been mentioned?
Also, it seems they were – my guess - well above Vr when they rejected.
Since they must have been light, acceleration would have been rapid.
The tail area was pretty well wiped out but the jackscrew for the stabilizer should still be intact.
Also, it seems they were – my guess - well above Vr when they rejected.
Since they must have been light, acceleration would have been rapid.
The tail area was pretty well wiped out but the jackscrew for the stabilizer should still be intact.
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Obama,
Don't think anybody is missing the point here, we know from the CVR they had a "Control issue" and elected to abort. What that issue was is presently unknown and hence a source of conjecture.
Likewise the overrun, given the presumably light take-off weight of the aircraft and seemingly more than adequate runway length and overrun area which was almost double the required BFL naturally causes one to wonder if there was another failure that caused the overrun, although as I posted previously I now think the overrun was purely a result of the very late, high speed abort.
Don't think anybody is missing the point here, we know from the CVR they had a "Control issue" and elected to abort. What that issue was is presently unknown and hence a source of conjecture.
Likewise the overrun, given the presumably light take-off weight of the aircraft and seemingly more than adequate runway length and overrun area which was almost double the required BFL naturally causes one to wonder if there was another failure that caused the overrun, although as I posted previously I now think the overrun was purely a result of the very late, high speed abort.
@Astra
I think you may be correct in the idea the over run was from a very late, high speed abort.
As mentioned earlier, maybe an aborted-abort? They have a control issue, think they have it solved, but no they don't?
I know this was a very experienced crew, but something along those lines is probably going to show up when the CVR and FDR info is released.
As mentioned earlier, maybe an aborted-abort? They have a control issue, think they have it solved, but no they don't?
I know this was a very experienced crew, but something along those lines is probably going to show up when the CVR and FDR info is released.
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Preliminary report has been posted by the NTSB
Preliminary Report: Crash on takeoff of Gulfstream Aerospace Corporation G-IV, Bedford, MA, May 31, 2014
Preliminary Report: Crash on takeoff of Gulfstream Aerospace Corporation G-IV, Bedford, MA, May 31, 2014
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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 gust lock handle, located on the right side of the control pedestal, was found in the forward (OFF) position, and the elevator gust lock latch was found not engaged.
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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 gust lock handle, located on the right side of the control pedestal, was found in the forward (OFF) position, and the elevator gust lock latch was found not engaged.
I had a non-rotation event happen to me once at V-R. Let me tell you, it takes a few seconds to comprehend that the aircraft did not rotate. I did manage to get the aircraft in the air right at the end of the runway by using full aft yoke and applying up trim at the same time.
If I had not been able to get airborne, we'd gone into a river at a very high rate of speed. Stopping on the remaining runway was out of question at V-R, there was not enough runway left to get the aircraft stopped on.
This was in a Westwind II and it was a forward CG issue that I was unaware of. Still would have been my fault if we had crashed.
would this be it? Review of FDR data parameters associated with the flight control su
Review of FDR data parameters associated with the flight control surface positions did not reveal any movement consistent with a flight control check prior to the commencement of the takeoff roll.
That could be important.
That could be important.
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Prelim. NTSB Report snip...
"Review of FDR data parameters associated with the flight control surface positions did not reveal any movement consistent with a flight control check prior to the commencement of the takeoff roll."
It just goes to show how important these checks are.
Very skilled and experienced pilots.....
"Review of FDR data parameters associated with the flight control surface positions did not reveal any movement consistent with a flight control check prior to the commencement of the takeoff roll."
It just goes to show how important these checks are.
Very skilled and experienced pilots.....
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Copied and pasted from a G550 after engine start checklist. (A GIV would be essentially the same)
3. EMERGENCY POWER ..............
4. DOORS ..........................................................CL OSED
5. APU .............................................. ON / AS REQUIRED
6. BLEED AIR Control Panel ...................................... SET
7. FUEL SYSTEM Panel ............................................ SET
8. COWL ANTI-ICE (2) / WING ANTI-ICE (2) ....... AS REQ
A. L / R COWL / WING ANTI-ICE ................................
..................................... ON (MANUALLY SELECT)
B. ³$I´ IFRQ LQ 7G7 GaJH ......................... DISPLAYED
C. Cowl Anti-Ice / Wing Anti-Ice, L-R Messages .......
........................................................... DISPLAYED
D. L / R COWL / WING ANTI-ICE ................................
.......................................... AUTO / AS REQUIRED
E. ³$I´ IFRQ aQG &$6 0HVVaJHV ........................... OFF
9. ANTI-ICE HTR (4) .................................................... ON
10. WINDSHIELD HEAT (2) ........................................... ON
11. CABIN PRESSURE AUTO / SEMI ...................... AUTO
12. Flight Controls 2/3 Synoptic Display ................ SELECT
13. Ground Spoilers (First Flight of Day) ............ CHECKED
14. Stall Barrier (First Flight of Day) ........................... TEST
15. Flight Controls / Bungees ............................. CHECKED
16. NOSE WHEEL STEERING POWER ........................ ON
17. YAW DAMP .......................................................... ENG
18 Standby Electrical Power System (HMG) .......... CHECK
Note item 15, " Flight Control / Bungees" check. Required on every flight
.
Also many Gulfstream crews perform this check as a "Line up" check as well.
It would seem that this unfortunate crew may have missed this critical check.
A copy of the NTSB preliminary report was just sent out company wide by both our Chief Pilot and our Director of Maintenance, I foresee a mandatory control check being required as a "line up" item for all aircraft in our fleet in the very near future.
3. EMERGENCY POWER ..............
4. DOORS ..........................................................CL OSED
5. APU .............................................. ON / AS REQUIRED
6. BLEED AIR Control Panel ...................................... SET
7. FUEL SYSTEM Panel ............................................ SET
8. COWL ANTI-ICE (2) / WING ANTI-ICE (2) ....... AS REQ
A. L / R COWL / WING ANTI-ICE ................................
..................................... ON (MANUALLY SELECT)
B. ³$I´ IFRQ LQ 7G7 GaJH ......................... DISPLAYED
C. Cowl Anti-Ice / Wing Anti-Ice, L-R Messages .......
........................................................... DISPLAYED
D. L / R COWL / WING ANTI-ICE ................................
.......................................... AUTO / AS REQUIRED
E. ³$I´ IFRQ aQG &$6 0HVVaJHV ........................... OFF
9. ANTI-ICE HTR (4) .................................................... ON
10. WINDSHIELD HEAT (2) ........................................... ON
11. CABIN PRESSURE AUTO / SEMI ...................... AUTO
12. Flight Controls 2/3 Synoptic Display ................ SELECT
13. Ground Spoilers (First Flight of Day) ............ CHECKED
14. Stall Barrier (First Flight of Day) ........................... TEST
15. Flight Controls / Bungees ............................. CHECKED
16. NOSE WHEEL STEERING POWER ........................ ON
17. YAW DAMP .......................................................... ENG
18 Standby Electrical Power System (HMG) .......... CHECK
Note item 15, " Flight Control / Bungees" check. Required on every flight
.
Also many Gulfstream crews perform this check as a "Line up" check as well.
It would seem that this unfortunate crew may have missed this critical check.
A copy of the NTSB preliminary report was just sent out company wide by both our Chief Pilot and our Director of Maintenance, I foresee a mandatory control check being required as a "line up" item for all aircraft in our fleet in the very near future.
Last edited by Astra driver; 13th Jun 2014 at 18:39. Reason: Attempting to clean up copy and paste