Bombardier Accident at Teterboro
Join Date: Mar 2004
Location: Canada
Age: 56
Posts: 46
Likes: 0
Received 0 Likes
on
0 Posts
I dont want to speculate here, simply talk systems.
The Autopilot on a CL600 can and will engage on the ground exactly as CLDriver mentionned. As a mather of fact, I have spoke to 3 different crew during my day as a FSI instructor who had a similiar happen. One of the crew had a jammed elevator on take off, the flying pilot could not rotate. For no reason, he looked at his attitude indicator and found his flight director was no longer in "Go Around" mode but came down to match the airplane's level attitude. He press the G/A switch again and flew away. The other 2 crew I spoke to realized the autopilot was engaged before break release. I am not saying this is what happened here, just one of the possibilities. But any 600 and 601-1a driver will tell you, the yaw damper is nautorious for kicking out on the ground.
As for the ice on the stab scenario, the CL60 has hydraulically operated flight controls with 2 PCUs (power control unit) on each side of the elevator. Each PCU is supplied 3000psi of hydraulic pressure, which is certainly sufficient to break any ice that may have formed. There have been "frozen controls" incidents on the CL before, but the freezing happened during prolongue flights which departed from a high humidity area. In most cases (not to say all) the freezing occured in the cables connecting the yoke to the actual PCUs.
A flight control check would find any control freezing, but would not help in finding an auopilot engagement on the ground since it probably occured after the check. A fair amount of CL pilots will keep their left hand on the nose-wheel steering tiler below 80kias, leaving the yoke to the non-flying pilot. If this "theory" of ours hold to be true, this may have been a contributing factor. Personally, I like holding my own yoke and give my own wind input. Nothing wrong with either, simply pilot technique.
Cheers,
D
CL601-3R
The Autopilot on a CL600 can and will engage on the ground exactly as CLDriver mentionned. As a mather of fact, I have spoke to 3 different crew during my day as a FSI instructor who had a similiar happen. One of the crew had a jammed elevator on take off, the flying pilot could not rotate. For no reason, he looked at his attitude indicator and found his flight director was no longer in "Go Around" mode but came down to match the airplane's level attitude. He press the G/A switch again and flew away. The other 2 crew I spoke to realized the autopilot was engaged before break release. I am not saying this is what happened here, just one of the possibilities. But any 600 and 601-1a driver will tell you, the yaw damper is nautorious for kicking out on the ground.
As for the ice on the stab scenario, the CL60 has hydraulically operated flight controls with 2 PCUs (power control unit) on each side of the elevator. Each PCU is supplied 3000psi of hydraulic pressure, which is certainly sufficient to break any ice that may have formed. There have been "frozen controls" incidents on the CL before, but the freezing happened during prolongue flights which departed from a high humidity area. In most cases (not to say all) the freezing occured in the cables connecting the yoke to the actual PCUs.
A flight control check would find any control freezing, but would not help in finding an auopilot engagement on the ground since it probably occured after the check. A fair amount of CL pilots will keep their left hand on the nose-wheel steering tiler below 80kias, leaving the yoke to the non-flying pilot. If this "theory" of ours hold to be true, this may have been a contributing factor. Personally, I like holding my own yoke and give my own wind input. Nothing wrong with either, simply pilot technique.
Cheers,
D
CL601-3R
Join Date: Jun 2002
Location: Slaving away in front of multiple LCDs, somewhere in the USA
Age: 69
Posts: 174
Likes: 0
Received 0 Likes
on
0 Posts
Apparently another aircraft of the same type had a similar abort back in December 2003...
(-23) N95EB A CANADAIR CL-600 ON AN IFR FLIGHT PLAN, DESTINATION LAS VEGAS, NV. ATTEMPTED A TAKEOFF FROM RUNWAY 24 AT KTEB. DURING THE TAKEOFF RUN PILOT REPORTED A NORMAL ACCELERATION TO ROTATION SPEED. WHEN HE ATTEMPTED TO PULL BACK ON CONTROL YOKE AIRCRAFT DID NOT RESPOND. THE PIC ELECTED TO ABORT THE TAKEOFF, RAN OFF END OF RUNWAY 24 IN MUD. EMERGENCY EVACUATION WAS INITIATED, WITH NO INJURIES. ^PRIVACY DATA OMITTED^
https://www.nasdac.faa.gov/pls/nasda...639G&NARR_VAR=
The NTSB report:
NTSB Identification: NYC04IA054.
The docket is stored in the Docket Management System (DMS). Please contact Public Inquiries
14 CFR Part 91: General Aviation
Incident occurred Tuesday, December 16, 2003 in Teterboro, NJ
Probable Cause Approval Date: 12/3/2004
Aircraft: Canadair CL-600, registration: N95EB
Injuries: 2 Uninjured.
Earlier in the day, a different flightcrew performed a successful aborted takeoff in the incident airplane. The aborted takeoff occurred with seven to nine passengers on board, at 139 knots; when the flightcrew was unable to rotate the airplane. The only difference between that aborted takeoff, and the uneventful previous flight, was the addition of 3,000 to 4,000 pounds of fuel. Following that aborted takeoff, the airplane underwent a maintenance inspection which did not reveal any discrepancies pertaining to the inability to rotate. The airplane was then returned to service. When the incident captain arrived at the airport, he was informed of the previous aborted takeoff. The incident captain attempted a takeoff on a shorter runway at the airport. During rotation, the airplane did not respond to elevator inputs, and the captain aborted the takeoff. The airplane then traveled off the end of the runway and came to rest in mud. Following the overrun, the incident captain failed to produce a weight and balance calculation, or accurate count of passengers on board at the time. The wind was reported as variable at 4 knots. When asked why he chose a shorter runway to attempt the takeoff, the incident captain reported that it was the runway in use at the time. The aircraft manufacturer inspected the airplane, and did not find any discrepancies pertaining to the aborted takeoff. The manufacturer also computed two weight and balance calculations for the incident takeoff. Both calculations revealed that the airplane was above the maximum gross takeoff weight, and outside the forward center-of-gravity envelope. Subsequently, the airplane tookoff with no passengers on board, and flew uneventfully to another airport.
The National Transportation Safety Board determines the probable cause(s) of this incident as follows:
The captain's inadequate preflight planning, which resulted in an overrun during an aborted takeoff.
National Transportation Safety Board
Washington, DC 20594
(-23) N95EB A CANADAIR CL-600 ON AN IFR FLIGHT PLAN, DESTINATION LAS VEGAS, NV. ATTEMPTED A TAKEOFF FROM RUNWAY 24 AT KTEB. DURING THE TAKEOFF RUN PILOT REPORTED A NORMAL ACCELERATION TO ROTATION SPEED. WHEN HE ATTEMPTED TO PULL BACK ON CONTROL YOKE AIRCRAFT DID NOT RESPOND. THE PIC ELECTED TO ABORT THE TAKEOFF, RAN OFF END OF RUNWAY 24 IN MUD. EMERGENCY EVACUATION WAS INITIATED, WITH NO INJURIES. ^PRIVACY DATA OMITTED^
https://www.nasdac.faa.gov/pls/nasda...639G&NARR_VAR=
The NTSB report:
NTSB Identification: NYC04IA054.
The docket is stored in the Docket Management System (DMS). Please contact Public Inquiries
14 CFR Part 91: General Aviation
Incident occurred Tuesday, December 16, 2003 in Teterboro, NJ
Probable Cause Approval Date: 12/3/2004
Aircraft: Canadair CL-600, registration: N95EB
Injuries: 2 Uninjured.
Earlier in the day, a different flightcrew performed a successful aborted takeoff in the incident airplane. The aborted takeoff occurred with seven to nine passengers on board, at 139 knots; when the flightcrew was unable to rotate the airplane. The only difference between that aborted takeoff, and the uneventful previous flight, was the addition of 3,000 to 4,000 pounds of fuel. Following that aborted takeoff, the airplane underwent a maintenance inspection which did not reveal any discrepancies pertaining to the inability to rotate. The airplane was then returned to service. When the incident captain arrived at the airport, he was informed of the previous aborted takeoff. The incident captain attempted a takeoff on a shorter runway at the airport. During rotation, the airplane did not respond to elevator inputs, and the captain aborted the takeoff. The airplane then traveled off the end of the runway and came to rest in mud. Following the overrun, the incident captain failed to produce a weight and balance calculation, or accurate count of passengers on board at the time. The wind was reported as variable at 4 knots. When asked why he chose a shorter runway to attempt the takeoff, the incident captain reported that it was the runway in use at the time. The aircraft manufacturer inspected the airplane, and did not find any discrepancies pertaining to the aborted takeoff. The manufacturer also computed two weight and balance calculations for the incident takeoff. Both calculations revealed that the airplane was above the maximum gross takeoff weight, and outside the forward center-of-gravity envelope. Subsequently, the airplane tookoff with no passengers on board, and flew uneventfully to another airport.
The National Transportation Safety Board determines the probable cause(s) of this incident as follows:
The captain's inadequate preflight planning, which resulted in an overrun during an aborted takeoff.
National Transportation Safety Board
Washington, DC 20594
Last edited by SeniorDispatcher; 7th Feb 2005 at 14:35.
Join Date: Jun 2002
Location: Slaving away in front of multiple LCDs, somewhere in the USA
Age: 69
Posts: 174
Likes: 0
Received 0 Likes
on
0 Posts
The only info I had was what I posted, but I think its wording is a little confusing...
>>>The only difference between that aborted takeoff, and the uneventful previous flight, was the addition of 3,000 to 4,000 pounds of fuel. Following that aborted takeoff, the airplane underwent a maintenance inspection which did not reveal any discrepancies pertaining to the inability to rotate. The airplane was then returned to service. When the incident captain arrived at the airport, he was informed of the previous aborted takeoff. The incident captain attempted a takeoff on a shorter runway at the airport. During rotation, the airplane did not respond to elevator inputs, and the captain aborted the takeoff.
The way I interpret it is....
1/ There was a normal flight (#1)
2/ There was another flight (#2) that was 3,000-4,000 lbs heavier than that normal flight, and they aborted. Aircraft checked out mechanically and all supposedly OK.
3/ There was another flight (#3) and it still was 3,000-4,000 lbs. heavier than flight #1. The crew of #2 briefed the crew of #3, and crew #3 had to do their own abort and went off in the mud...
By its absence in the report, once could presume that after flight #2, only the mechanical aspects were checked, and not the W&B figures..
>>>The only difference between that aborted takeoff, and the uneventful previous flight, was the addition of 3,000 to 4,000 pounds of fuel. Following that aborted takeoff, the airplane underwent a maintenance inspection which did not reveal any discrepancies pertaining to the inability to rotate. The airplane was then returned to service. When the incident captain arrived at the airport, he was informed of the previous aborted takeoff. The incident captain attempted a takeoff on a shorter runway at the airport. During rotation, the airplane did not respond to elevator inputs, and the captain aborted the takeoff.
The way I interpret it is....
1/ There was a normal flight (#1)
2/ There was another flight (#2) that was 3,000-4,000 lbs heavier than that normal flight, and they aborted. Aircraft checked out mechanically and all supposedly OK.
3/ There was another flight (#3) and it still was 3,000-4,000 lbs. heavier than flight #1. The crew of #2 briefed the crew of #3, and crew #3 had to do their own abort and went off in the mud...
By its absence in the report, once could presume that after flight #2, only the mechanical aspects were checked, and not the W&B figures..
Join Date: May 1999
Location: USA
Posts: 195
Likes: 0
Received 0 Likes
on
0 Posts
"A pure CLEAN WING philosophy would leave absolutely no room for confusion or creative misinterpretation."
Sounds fine in theory - but how can we be sure that we really have a clean airframe? It has been proven (by Canadians) that a visual inspection through a window just prior to t/o means squat. Nothing to do with this particular case, but an aircraft's performance and handling cannot be guaranteed these days in light of new information abot a piltos inability to make a proper visual determination in certain circumstances.
About time someone invented a laser device for figuring how much ice is really remaining on an airframe. The all we have to do is decide how much is acceptable.
Sounds fine in theory - but how can we be sure that we really have a clean airframe? It has been proven (by Canadians) that a visual inspection through a window just prior to t/o means squat. Nothing to do with this particular case, but an aircraft's performance and handling cannot be guaranteed these days in light of new information abot a piltos inability to make a proper visual determination in certain circumstances.
About time someone invented a laser device for figuring how much ice is really remaining on an airframe. The all we have to do is decide how much is acceptable.
Join Date: Dec 1998
Location: England
Posts: 242
Likes: 0
Received 0 Likes
on
0 Posts
ICING SOLUTIONS (Discrad the 1940's Anti and de-icing Technologies)
Statement from the NASA Glenn Icing Research Site at link
Background of Collaborative SLD Research
Airworthiness authorities are considering the release of an operational rule affecting aircraft operations in Supercooled Large Droplet (SLD) icing conditions. Manufacturers will be required to demonstrate their aircraft can operate in SLD conditions for some period of time to facilitate a safe exit from this hazardous condition.
The Blasering Away Solution to Anti- & De-Ice
Article One
The NTSB alert warns pilots that ice contamination on the upper surface compromises the wing's lift-generating function:
a. "Research results have shown that fine particles of frost or ice, the size of a grain of table salt and distributed as sparsely as one per square centimeter over an airplane wing's upper surface can destroy enough lift to prevent that aircraft from taking off."
b. "It is also possible that many pilots believe ... They can simply 'power through' any performance degradation that might result from almost imperceptible amounts of upper wing surface ice accumulation. However, engine power will not prevent a stall and loss of control at lift off, where the highest angles of attack are normally achieved."
c. "Further, small patches of almost imperceptible ice or frost can result in localized, asymmetrical stalls on the wing, which can result in roll control problems during lift off."
d. "It may be difficult for a pilot to see ice on the upper wing surface from the ground or through the cockpit or other windows. Further, frost, snow, and rime ice can be very difficult to detect on a white upper wing surface and clear ice can be difficult to detect on an upper wing surface of any color. However, it is critically important to ensure, by any means necessary, that the upper wing surface is clear of contamination before takeoff [by] visual and tactile inspections."
To all of these precautionary procedures, a plug for thermal de-icing with lasers bears mention once again (see ASW, Nov. 10, 2003). When one:
1. Considers the cost of de-icing with fluids (on top of which one can stack all the environmental concerns for getting rid of "spent" de-icing fluid and the fumes in the cockpit plus APU problems resulting from de-icing fluid getting where it's not supposed to go), and
2. Hears about these pilots taking a chance, and looks at the hold-over rules (for starting the process all over again), plus
3. Recalls all the accidents caused by failure to de-ice, and inability of inflight anti-icing systems to cope with SLD
4. Notes all the ground accidents caused by de-icing rigs striking aircraft, then .....
Thermal laser de-icing on the ground (and thermal laser anti-icing airborne) might prove to be a real blessing and a big boon to safety.
Article Two
Thermal laser wiping: The theory is that a twin laser unit sits atop the cockpit of a high-wing turboprop (and another under the nose of a low-wing turboprop) in an ice-guarded rear-facing cupola. It is memory-mapped with the airplane's anatomic profile.
The low-power laser continuously measures (via a mensuration mapping software program) the aircraft's profile, until it detects an anomaly associated with ice accretion. With the high-power laser armed by the ice-detector, it then commences thermal lasering of the aircraft's leading edges, engine intakes, propellers, pitots and forward wing sections. The cupola mounted above the flight deck would also handle the empennage.
Such a system might weigh less than the unaerodynamic boots. Electric power demand might not be that great, as heavy-duty capacitors could be charged up over a period of time and then discharged for the periodic phased-array attacks on lodged ice. As per the standard inflation cycle for de-icer boots, the lasers could alternate phase (top cupola/bottom cupola) and run a 30 seconds on/30 seconds off cycle.
Maybe this system could be called the Laissez-faire, a play on the word laser which might appeal to the French manufacturer of the ATR-72 (Laissez-faire = Non- interference in the affairs of others, as in 'ice go away').
Bonuses?
1. Avian Interferometer (bird deflector). When not in use in ice-detect and -destroy mode, both cupolas swing 180 degrees and search the ahead predicted flight-path sector for avian intruders (and zap them - with the thermal laser). Effect would be like focussing a magnifying glass on someone's neck (when they're not looking). Birds predictably dive for speed and clear the flight-path.
2. If the weapons techs feel inspired, maybe they could inbuild a MANPADS "detect and destroy" capability or variant?
Background of Collaborative SLD Research
Airworthiness authorities are considering the release of an operational rule affecting aircraft operations in Supercooled Large Droplet (SLD) icing conditions. Manufacturers will be required to demonstrate their aircraft can operate in SLD conditions for some period of time to facilitate a safe exit from this hazardous condition.
The Blasering Away Solution to Anti- & De-Ice
Article One
The NTSB alert warns pilots that ice contamination on the upper surface compromises the wing's lift-generating function:
a. "Research results have shown that fine particles of frost or ice, the size of a grain of table salt and distributed as sparsely as one per square centimeter over an airplane wing's upper surface can destroy enough lift to prevent that aircraft from taking off."
b. "It is also possible that many pilots believe ... They can simply 'power through' any performance degradation that might result from almost imperceptible amounts of upper wing surface ice accumulation. However, engine power will not prevent a stall and loss of control at lift off, where the highest angles of attack are normally achieved."
c. "Further, small patches of almost imperceptible ice or frost can result in localized, asymmetrical stalls on the wing, which can result in roll control problems during lift off."
d. "It may be difficult for a pilot to see ice on the upper wing surface from the ground or through the cockpit or other windows. Further, frost, snow, and rime ice can be very difficult to detect on a white upper wing surface and clear ice can be difficult to detect on an upper wing surface of any color. However, it is critically important to ensure, by any means necessary, that the upper wing surface is clear of contamination before takeoff [by] visual and tactile inspections."
To all of these precautionary procedures, a plug for thermal de-icing with lasers bears mention once again (see ASW, Nov. 10, 2003). When one:
1. Considers the cost of de-icing with fluids (on top of which one can stack all the environmental concerns for getting rid of "spent" de-icing fluid and the fumes in the cockpit plus APU problems resulting from de-icing fluid getting where it's not supposed to go), and
2. Hears about these pilots taking a chance, and looks at the hold-over rules (for starting the process all over again), plus
3. Recalls all the accidents caused by failure to de-ice, and inability of inflight anti-icing systems to cope with SLD
4. Notes all the ground accidents caused by de-icing rigs striking aircraft, then .....
Thermal laser de-icing on the ground (and thermal laser anti-icing airborne) might prove to be a real blessing and a big boon to safety.
Article Two
Thermal laser wiping: The theory is that a twin laser unit sits atop the cockpit of a high-wing turboprop (and another under the nose of a low-wing turboprop) in an ice-guarded rear-facing cupola. It is memory-mapped with the airplane's anatomic profile.
The low-power laser continuously measures (via a mensuration mapping software program) the aircraft's profile, until it detects an anomaly associated with ice accretion. With the high-power laser armed by the ice-detector, it then commences thermal lasering of the aircraft's leading edges, engine intakes, propellers, pitots and forward wing sections. The cupola mounted above the flight deck would also handle the empennage.
Such a system might weigh less than the unaerodynamic boots. Electric power demand might not be that great, as heavy-duty capacitors could be charged up over a period of time and then discharged for the periodic phased-array attacks on lodged ice. As per the standard inflation cycle for de-icer boots, the lasers could alternate phase (top cupola/bottom cupola) and run a 30 seconds on/30 seconds off cycle.
Maybe this system could be called the Laissez-faire, a play on the word laser which might appeal to the French manufacturer of the ATR-72 (Laissez-faire = Non- interference in the affairs of others, as in 'ice go away').
Bonuses?
1. Avian Interferometer (bird deflector). When not in use in ice-detect and -destroy mode, both cupolas swing 180 degrees and search the ahead predicted flight-path sector for avian intruders (and zap them - with the thermal laser). Effect would be like focussing a magnifying glass on someone's neck (when they're not looking). Birds predictably dive for speed and clear the flight-path.
2. If the weapons techs feel inspired, maybe they could inbuild a MANPADS "detect and destroy" capability or variant?
Join Date: Jan 2001
Location: Dallas, TX USA
Posts: 739
Likes: 0
Received 0 Likes
on
0 Posts
Seniordispatcher, the full narrative is located here:
Full Narrative
It appears as you say, that flight #2 was overweight the same as flight #3. I find it interesting that two separate flight crews failed to determine that the aircraft was overweight.
Full Narrative
It appears as you say, that flight #2 was overweight the same as flight #3. I find it interesting that two separate flight crews failed to determine that the aircraft was overweight.
Join Date: Dec 1998
Location: England
Posts: 242
Likes: 0
Received 0 Likes
on
0 Posts
Slight difference between not being able to get the nose off due to "overweight and too far forward a CofG" and "not being able to get any backstick".
But having said that, in the earlier case temps were 41 degs F and in the warehouse overrun only 20 to 22 degs F (with both having a near full load of pax). Both would have had a similar fuel load (15,000lbs) - from what I can ascertain. So if the 24 overrun was overweight it's likely that the 06 warehousing take-off attempt would have been also.
But having said that, in the earlier case temps were 41 degs F and in the warehouse overrun only 20 to 22 degs F (with both having a near full load of pax). Both would have had a similar fuel load (15,000lbs) - from what I can ascertain. So if the 24 overrun was overweight it's likely that the 06 warehousing take-off attempt would have been also.
Join Date: Sep 2002
Location: La Belle Province
Posts: 2,179
Likes: 0
Received 0 Likes
on
0 Posts
No, because the issue was "over MTOW" not "over MTOW as limited by WAT". So the old case was over at any temp.
I don't think you can deduce from the older case that the more recent accident was overweight. There's no evidence I'm aware of that the more recent aircraft was overloaded, which is what the above NTSB quote certainly implies for the earlier case.
All it tells you is that aircraft outside the forward end of the cg envelope may fail to rotate; it doesn't allow the conclusion that all failures to rotate must lie outside the weight/cg envelope.
Both calculations revealed that the airplane was above the maximum gross takeoff weight, and outside the forward center-of-gravity envelope.
All it tells you is that aircraft outside the forward end of the cg envelope may fail to rotate; it doesn't allow the conclusion that all failures to rotate must lie outside the weight/cg envelope.
Join Date: Jan 2001
Location: Dallas, TX USA
Posts: 739
Likes: 0
Received 0 Likes
on
0 Posts
MFS is correct. In the earlier incidents, the pilots most likely pulled the yoke all the way back and the aircraft failed to rotate due to being overweight and forward of the CG limit. In the current case, the pilots tried to pull the yoke back, and it wouldn't go back more than an inch (thus failng to rotate), so the cause should be quite different from these earlier incidents.
I don't follow the linkage between weight, CG balance, and failure to rotate with the accident which is the subject of this thread where the pilot claimed that the stick mechanically wouldn't even pull back.
Are all these discussions putting aside that report or are we just filling space here waiting for a new fact to emerge?
Are all these discussions putting aside that report or are we just filling space here waiting for a new fact to emerge?
Join Date: Sep 2002
Location: La Belle Province
Posts: 2,179
Likes: 0
Received 0 Likes
on
0 Posts
The only linkage between the earlier Teterboro incident and the most recent one is that it shows that loading problems can contribute towards a failure to rotate.
As I understand it, the NTSB have stated a speed of 153kts was on the FDR, which is significantly above the nominal Vr. Under otherwise normal circumstances, at that kind of overspeed it's rather difficult to prevent an aircraft from rotating - it's nominally trimmed for V2, after all, and that's pretty much the speed right there. So even with a control restriction (and the pilot implies there was at least some motion) one might expect a normally loaded Challenger to have got airborne. Therefore, what we may well find in due course is that there was a loading issue AS WELL. (It's quite rare that one thing alone shows up as a cause - usually designs are such that several things have to 'go wrong')
What the earlier incident also shows is that the Challenger can be misladen so as to be heavy and forward. Since it sounds like both aircraft were quite similarly loaded (in the sense that both had quite full cabins - of course the fuel loads might not be similar) it IS possible the cg was also quite far forward on the latest flight. Whether it was outside the envelope is pure speculation, but even forward and INSIDE the envelope is of course harder to rotate.
As I understand it, the NTSB have stated a speed of 153kts was on the FDR, which is significantly above the nominal Vr. Under otherwise normal circumstances, at that kind of overspeed it's rather difficult to prevent an aircraft from rotating - it's nominally trimmed for V2, after all, and that's pretty much the speed right there. So even with a control restriction (and the pilot implies there was at least some motion) one might expect a normally loaded Challenger to have got airborne. Therefore, what we may well find in due course is that there was a loading issue AS WELL. (It's quite rare that one thing alone shows up as a cause - usually designs are such that several things have to 'go wrong')
What the earlier incident also shows is that the Challenger can be misladen so as to be heavy and forward. Since it sounds like both aircraft were quite similarly loaded (in the sense that both had quite full cabins - of course the fuel loads might not be similar) it IS possible the cg was also quite far forward on the latest flight. Whether it was outside the envelope is pure speculation, but even forward and INSIDE the envelope is of course harder to rotate.
Join Date: Jan 2001
Location: Dallas, TX USA
Posts: 739
Likes: 0
Received 0 Likes
on
0 Posts
With the apparent flight control (elevator) restriction experienced by these pilots, if the aircraft had somehow managed to become airborne, the outcome could have been disasterous. Far better to hit the warehouse while on the ground, then to hit the ground from any altitude without pitch control.
If this problem was rooted in an accidental activation of the auto-pilot (while correcting a yaw damper trip) as some have suggested, then the implications of a successful liftoff under these circumstances will have to be expanded upon by those who know the systems better than I.
If this problem was rooted in an accidental activation of the auto-pilot (while correcting a yaw damper trip) as some have suggested, then the implications of a successful liftoff under these circumstances will have to be expanded upon by those who know the systems better than I.
It seems to me we also spent a good deal of time speculating about the contribution of overloading for the USAIR accident. Ultimately it turned out to be 98% mechanical and just a hint of overloading.
Remove the mechanical from the equation and it flies.
Remove the mechanical from the equation and it flies.
Join Date: Mar 2004
Location: Canada
Age: 56
Posts: 46
Likes: 0
Received 0 Likes
on
0 Posts
Effect of CofG on rotation.
The Challenger's stabilizer is quite larger then the elevetor (as shown by UNCTUOUS' pictures on page 5). As with most jet, the Challenger pitch trim system moves the stabilizer.
Consider an airplane loaded at its maximum foreward CofG limit, at Maximum takeoff weight, in a high and hot environement. If the STAB trim is not set properly for the CofG, the airplane will be dificult to rotate. I have seen a few crews run off the runway (in the sim) in these conditions.
But KTEB is almost at sea level, the OAT was below freezing. On my CL, with 11pax and NBAA fuel to do the 700nm to Chicago the T/O weight would have been around 37500lbs. Not to far from the 600 MTOW of 41100lbs (the 3R I fly has a MTOW of 45100lbs), but not that close to the limit. On a CL, fuel affects the CofG much more then pax load. Unless he was tankering fuel, fuel would have been present only in the wings (the first 9800lbs go to the wings) causing a CofG far from the foreward limit.
Just my 2cents
D
The Challenger's stabilizer is quite larger then the elevetor (as shown by UNCTUOUS' pictures on page 5). As with most jet, the Challenger pitch trim system moves the stabilizer.
Consider an airplane loaded at its maximum foreward CofG limit, at Maximum takeoff weight, in a high and hot environement. If the STAB trim is not set properly for the CofG, the airplane will be dificult to rotate. I have seen a few crews run off the runway (in the sim) in these conditions.
But KTEB is almost at sea level, the OAT was below freezing. On my CL, with 11pax and NBAA fuel to do the 700nm to Chicago the T/O weight would have been around 37500lbs. Not to far from the 600 MTOW of 41100lbs (the 3R I fly has a MTOW of 45100lbs), but not that close to the limit. On a CL, fuel affects the CofG much more then pax load. Unless he was tankering fuel, fuel would have been present only in the wings (the first 9800lbs go to the wings) causing a CofG far from the foreward limit.
Just my 2cents
D
Last edited by fougapilot; 11th Feb 2005 at 12:00.
Join Date: Mar 2000
Location: Arizona USA
Posts: 8,571
Likes: 0
Received 0 Likes
on
0 Posts
Just for info...
Does any current (or out of production) business jet use an all-moving stab, for primary pitch control, ala the Lockheed TriStar?
In the tri-motor, that stab is very powerful, and mis-trimmed/mis loaded conditions are handled quite well...according to my experience, and that of prior Lockheed production test pilots.
Does any current (or out of production) business jet use an all-moving stab, for primary pitch control, ala the Lockheed TriStar?
In the tri-motor, that stab is very powerful, and mis-trimmed/mis loaded conditions are handled quite well...according to my experience, and that of prior Lockheed production test pilots.
Join Date: Mar 2000
Location: Obvious
Age: 78
Posts: 301
Likes: 0
Received 0 Likes
on
0 Posts
Controls jammed or Yoke jammed - not a failure to rotate?
Aren't we losing sight of the fact that BOTH pilots claimed directly after the accident (and at their later FAA/NTSB interviews) that they couldn't get any usable backstick. Surely that is a different proposition to no rotation due to CofG too far forward or overweight or stab or trim mis-set?
Being unable to physically pull the yoke back points to something having happened after they did their control checks.
a. A knee-pad fell down between the seat and either yoke?
b. An elevator control restriction caused by something getting pat the stock standard boot at the base of each yoke?
c. A spanner left somewhere adjacent to the control runs that became dislodged and jammed the works.
d. A mechanical connection somewhere in the flight control circuit having jammed/become disconnected.
e. the autopilot having become inadvertently engaged (as described earlier - and being more likely)
Being unable to physically pull the yoke back points to something having happened after they did their control checks.
a. A knee-pad fell down between the seat and either yoke?
b. An elevator control restriction caused by something getting pat the stock standard boot at the base of each yoke?
c. A spanner left somewhere adjacent to the control runs that became dislodged and jammed the works.
d. A mechanical connection somewhere in the flight control circuit having jammed/become disconnected.
e. the autopilot having become inadvertently engaged (as described earlier - and being more likely)