Tripp
You think you hate it now...
From ANN:
quote:
Marine Corps MV-22 Sim Couldn't Prepare Pilots
The Marines are learning a little more about the April 8 VM-22 Osprey crash, each time they discover a little piece of new evidence; and they are sharing their findings with us, as Lt. Gen. Fred McCorkle, the Marine Corps' aviation chief, said he would. The data change a little from time to time; but the general feeling is going in one direction: the aircraft was probably descending too quickly -- and some other factors, none of them too severe by themselves, added up to disaster.
McCorkle released information last week that pointed to a too-rapid descent (quoting about 1700 fpm), which led to a "settling with power" situation, which may have been aggravated by the doomed plane's following within 200 feet of another Osprey. The right rotor lost lift first, and the ship tipped over, heading steeply into the ground.
The investigation originally took a hard look at the possibility of disorientation in this pitch-dark night exercise, while both pilots were wearing night vision equipment. As the discovery process built, though, there seemed less and less an NVG problem. Software and hardware problems were set aside early on in the investigation. The flight itself looks like the proximate cause.
The Osprey shouldn't descend at more than 800 fpm, at low forward airspeeds. The reports now say it was dropping at 1000 fpm. The data from the last few seconds show it was descending with a vertical component of 2100 fpm (a 24-mph downward component!) before it lost lift altogether and cascaded to the ground, killing nineteen Marines.
Investigators were able to retrieve flight data from the Crash Survivable Memory Unit. The MV-22 was among four that flew a mission at 9,500 ft. and then dropped to 5,000 ft. for the descent into Marana regional airport outside Tucson, according to Marine Corps reports. At 6 sec. before impact, the MV-22 was at 41 kt. and 350 ft. AGL. Two sec. later, the aircraft was at 37 kt. and 280 ft. [That's 2100 fpm --ed.] "At this time [the pilot] put in about 5-15 deg. bank angle to the right and a little bit of right rudder to stabilize his movement," McCorkle said. Three seconds before impact, the aircraft was at 245 ft. [that also, figures out to 2100 fpm --ed.] and 33 kt. At one sec. it had dropped to 210 ft. [there's that 2100 fpm descent again --ed.] and 30 kt.
"The data show . . . a high rate of descent at a relatively low forward air speed," McCorkle said. "These characteristics can lead to a condition known as power settling or vortex ring state. This can result in loss of lift. Power settling is a condition common to all helicopter flight and is now the main focus of the investigation." Power settling is the inability to stop a descent. Vortex ring state occurs when the velocity of air pushed down by the rotor equals the aircraft's rate of descent, he said. "When [the pilot] went into the 15-deg. angle of bank. . . he went into power settling," McCorkle said. "He was [already] in big trouble. The left wing then lifted and the right wing went down and the bank angle continued [to increase]. As soon as the aircraft started rolling over [due to the stall], he put in full left stick. [But] It would have been very difficult for him to recover at that point."
Additionally, a light tailwind, about 10kt, tended to further reduce the ship's airspeed to below 40kts. the pilot was apparently making a right turn, as well. The lift was gone.
Only a single segment of the flight envelope appears to have been exceeded, and that involved a too-rapid descent for the MV 22's low forward speed. The aircraft is restricted to 800 ft. per minute at altitudes below 500 ft. when under 40-kt. forward airspeed. During the last 4-5 sec. of flight, the aircraft was under 40 kt. airspeed. "We think he was over 1,000 ft. per minute all the way down on the descent," McCorkle said. [A week ago, the rate was reported at "1700 fpm" --ed.] "There is a warning [that in such conditions] you could put yourself into power settling."
Official sources explain: Marine Corps Commandant Gen. James Jones and Air Force Chief of Staff Gen. Mike Ryan have said they will make the first passenger-carrying flight in the aircraft. However, before training and the MV 22's operational evaluation resumes (in about 1-2 weeks, McCorkle estimated), V 22 development aircraft and a team of test pilots will try to duplicate the conditions that produced the crash except at altitudes high enough to allow recovery. The accident cannot be replicated in simulators because a vortex ring state has not been put into the systems' computers. The solution to power settling is to reduce power and push the aircraft's nose over to regain airspeed and lift, McCorkle said. So far, there is no way to warn a pilot of rotor stall
quote:
Marine Corps MV-22 Sim Couldn't Prepare Pilots
The Marines are learning a little more about the April 8 VM-22 Osprey crash, each time they discover a little piece of new evidence; and they are sharing their findings with us, as Lt. Gen. Fred McCorkle, the Marine Corps' aviation chief, said he would. The data change a little from time to time; but the general feeling is going in one direction: the aircraft was probably descending too quickly -- and some other factors, none of them too severe by themselves, added up to disaster.
McCorkle released information last week that pointed to a too-rapid descent (quoting about 1700 fpm), which led to a "settling with power" situation, which may have been aggravated by the doomed plane's following within 200 feet of another Osprey. The right rotor lost lift first, and the ship tipped over, heading steeply into the ground.
The investigation originally took a hard look at the possibility of disorientation in this pitch-dark night exercise, while both pilots were wearing night vision equipment. As the discovery process built, though, there seemed less and less an NVG problem. Software and hardware problems were set aside early on in the investigation. The flight itself looks like the proximate cause.
The Osprey shouldn't descend at more than 800 fpm, at low forward airspeeds. The reports now say it was dropping at 1000 fpm. The data from the last few seconds show it was descending with a vertical component of 2100 fpm (a 24-mph downward component!) before it lost lift altogether and cascaded to the ground, killing nineteen Marines.
Investigators were able to retrieve flight data from the Crash Survivable Memory Unit. The MV-22 was among four that flew a mission at 9,500 ft. and then dropped to 5,000 ft. for the descent into Marana regional airport outside Tucson, according to Marine Corps reports. At 6 sec. before impact, the MV-22 was at 41 kt. and 350 ft. AGL. Two sec. later, the aircraft was at 37 kt. and 280 ft. [That's 2100 fpm --ed.] "At this time [the pilot] put in about 5-15 deg. bank angle to the right and a little bit of right rudder to stabilize his movement," McCorkle said. Three seconds before impact, the aircraft was at 245 ft. [that also, figures out to 2100 fpm --ed.] and 33 kt. At one sec. it had dropped to 210 ft. [there's that 2100 fpm descent again --ed.] and 30 kt.
"The data show . . . a high rate of descent at a relatively low forward air speed," McCorkle said. "These characteristics can lead to a condition known as power settling or vortex ring state. This can result in loss of lift. Power settling is a condition common to all helicopter flight and is now the main focus of the investigation." Power settling is the inability to stop a descent. Vortex ring state occurs when the velocity of air pushed down by the rotor equals the aircraft's rate of descent, he said. "When [the pilot] went into the 15-deg. angle of bank. . . he went into power settling," McCorkle said. "He was [already] in big trouble. The left wing then lifted and the right wing went down and the bank angle continued [to increase]. As soon as the aircraft started rolling over [due to the stall], he put in full left stick. [But] It would have been very difficult for him to recover at that point."
Additionally, a light tailwind, about 10kt, tended to further reduce the ship's airspeed to below 40kts. the pilot was apparently making a right turn, as well. The lift was gone.
Only a single segment of the flight envelope appears to have been exceeded, and that involved a too-rapid descent for the MV 22's low forward speed. The aircraft is restricted to 800 ft. per minute at altitudes below 500 ft. when under 40-kt. forward airspeed. During the last 4-5 sec. of flight, the aircraft was under 40 kt. airspeed. "We think he was over 1,000 ft. per minute all the way down on the descent," McCorkle said. [A week ago, the rate was reported at "1700 fpm" --ed.] "There is a warning [that in such conditions] you could put yourself into power settling."
Official sources explain: Marine Corps Commandant Gen. James Jones and Air Force Chief of Staff Gen. Mike Ryan have said they will make the first passenger-carrying flight in the aircraft. However, before training and the MV 22's operational evaluation resumes (in about 1-2 weeks, McCorkle estimated), V 22 development aircraft and a team of test pilots will try to duplicate the conditions that produced the crash except at altitudes high enough to allow recovery. The accident cannot be replicated in simulators because a vortex ring state has not been put into the systems' computers. The solution to power settling is to reduce power and push the aircraft's nose over to regain airspeed and lift, McCorkle said. So far, there is no way to warn a pilot of rotor stall