Number 255
November 2000
Wake Vortex Hazard at Cruise Altitudes
Wake turbulence is commonly associated with Terminal Area arrival and departure operations. However, ASRS has received several recent reports that describe wake vortex incidents at cruise altitudes, with 10 miles or more in-trail separation between the involved aircraft. All the incidents appeared to occur in smooth air with little, or no, wind. More from the flight crew of a Fokker-100:
s …While in [North Atlantic] airspace, [our] MD-11 aircraft
was cleared from FL350 to FL340. The position was…10 miles ahead of [a] B-767 flight. [We] received a radio message from the 767 flight. It reported that it “almost rolled over” from the wake turbulence encountered at FL340. The 767 reported a slow roll to the right (15°) followed by a snap roll to the left until the pilot disconnected the autopilot and applied opposite control forces. The maximum bank angle was 30°. The 767 aircraft was climbing from FL330 to FL350 and became destabilized at FL340. Aircraft separation was 10 miles in trail. Both aircraft were in radar contact. The 767 was flying at Mach .80… The MD-11 airplane flew at FL340, Mach .82. The North Atlantic Minimum Navigation Performance Specifications (MNPS) implemented in March 1997 provide 1,000 foot vertical separation for aircraft between FL340 and FL390. If a revised ATC clearance is not possible for wake vortex avoidance, the pilot may establish contact with the other aircraft on 131.8 MHz, and one or both aircraft may initiate lateral offsets not to exceed 2 NM from the assigned route(s) or track(s). Offsetting aircraft are expected to notify ATC of their actions as soon as possible. ATC will not issue clearances for lateral offsets on its own initiative. Pacific Region vertical separation minima are specified in FAA Notice 7110.218, effective February 2000.
s Just prior to leveling off at FL330 – at about FL32.7 we
encountered moderate to severe rapid and instantaneous roll reversals and turbulence. We were in perfectly smooth air with no [FMS] wind and not anywhere near the jet stream as forecasted. We were about 17 NM in trail with a Heavy B767 that had previously overflown us in his faster climbout and speed capability. We immediately requested and received clearance to FL290. All systems and controls were normal. We strongly…suspect that in the calm air, this heavy aircraft’s vortices do not descend very fast – if at all – and at 17 miles in trail are only about one and on-half minutes behind. I recommend that all Operator’s Manuals be updated to reflect this wake vortex behavior at altitude in smooth air, which is very similar to their behavior in smooth air at low altitude with anticipated separation… A similar report was filed by a First Officer of a North Atlantic flight, whose descending aircraft may have caused a wake vortex problem for a climbing B-767:
The Case of the Phantom Load
ASRS recently received several flight crew reports of interest describing a widebody jet that thought it was airborne – while still on the ground. More details from the First Officer’s report:
s We were scheduled to fly a charter flight… We eventually
arrived at the aircraft [in early morning hours]. I performed the external aircraft preflight. When we approached the aircraft, the freight was in the process of being off-loaded from the main cargo deck. It was noted that there was no nosewheel strap or weight to hold the nose down. The Captain asked the load-master about this and was told there were none available and [he] assured us there would be no problem. We were expecting no freight in the upper cargo deck and very little in the forward belly. The preflight was normal. All doors were closed except for the main cargo door and left main cabin door (L1). We began the cockpit setup. All was normal until the main cargo door was closed. As it closed, numerous alerts came on. Neither of us had seen anything like this before. We called our maintenance personnel onboard. After removing power and resetting the aircraft, they restored everything to normal operation. I went back to close the L1 door. When I got back
to the cockpit, all the alerts had reappeared. We had maintenance come back onboard. They tried removing power again, but when it was reapplied, the stick-shakers activated. It was then that someone said it appeared the aircraft thought it was airborne. This did account for the alerts. Then one of the support people helping with the launch said that the nose strut was extended too far. He had experience with Air Force KC-10’s and said they couldn’t launch one with that much strut exposed. I went down and confirmed this. We realized that the Center of Gravity was too far aft. It was discovered that there were containers in A7 and A6, the most aft belly positions. The weight and balance showed an empty aircraft except for containers in F1 and F2, the most forward belly positions, weighing approximately 6300 pounds. At this point the…Captain directed [the load master] to reweigh the containers and load them in the proper positions. A new weight and balance form was brought to the aircraft and we then departed uneventfully.
ASRS Recently Issued Alerts On…
CL-65 inflight windshield failure A-300 uncommanded rudder movement at FL350 Mechanics’ misinterpretation of Piper gear kit instructions A runway signage problem at a major East Coast airport RB211 engine spinner fairing cracks found on two B-757s
A Monthly Safety Bulletin from
The Office of the NASA Aviation Safety Reporting System, P.O. Box 189, Moffett Field, CA 94035-0189 http://asrs.arc.nasa.gov/
September 2000 Report Intake
Air Carrier / Air Taxi Pilots General Aviation Pilots Controllers Cabin/Mechanics/Military/Other TOTAL 2236 623 106 183 3148
飞行翻译公司 www.aviation.cn 本文链接地址：美国ASRS安全公告CALLBACK cb_255.pdf
November 2000
Wake Vortex Hazard at Cruise Altitudes
Wake turbulence is commonly associated with Terminal Area arrival and departure operations. However, ASRS has received several recent reports that describe wake vortex incidents at cruise altitudes, with 10 miles or more in-trail separation between the involved aircraft. All the incidents appeared to occur in smooth air with little, or no, wind. More from the flight crew of a Fokker-100:
s …While in [North Atlantic] airspace, [our] MD-11 aircraft
was cleared from FL350 to FL340. The position was…10 miles ahead of [a] B-767 flight. [We] received a radio message from the 767 flight. It reported that it “almost rolled over” from the wake turbulence encountered at FL340. The 767 reported a slow roll to the right (15°) followed by a snap roll to the left until the pilot disconnected the autopilot and applied opposite control forces. The maximum bank angle was 30°. The 767 aircraft was climbing from FL330 to FL350 and became destabilized at FL340. Aircraft separation was 10 miles in trail. Both aircraft were in radar contact. The 767 was flying at Mach .80… The MD-11 airplane flew at FL340, Mach .82. The North Atlantic Minimum Navigation Performance Specifications (MNPS) implemented in March 1997 provide 1,000 foot vertical separation for aircraft between FL340 and FL390. If a revised ATC clearance is not possible for wake vortex avoidance, the pilot may establish contact with the other aircraft on 131.8 MHz, and one or both aircraft may initiate lateral offsets not to exceed 2 NM from the assigned route(s) or track(s). Offsetting aircraft are expected to notify ATC of their actions as soon as possible. ATC will not issue clearances for lateral offsets on its own initiative. Pacific Region vertical separation minima are specified in FAA Notice 7110.218, effective February 2000.
s Just prior to leveling off at FL330 – at about FL32.7 we
encountered moderate to severe rapid and instantaneous roll reversals and turbulence. We were in perfectly smooth air with no [FMS] wind and not anywhere near the jet stream as forecasted. We were about 17 NM in trail with a Heavy B767 that had previously overflown us in his faster climbout and speed capability. We immediately requested and received clearance to FL290. All systems and controls were normal. We strongly…suspect that in the calm air, this heavy aircraft’s vortices do not descend very fast – if at all – and at 17 miles in trail are only about one and on-half minutes behind. I recommend that all Operator’s Manuals be updated to reflect this wake vortex behavior at altitude in smooth air, which is very similar to their behavior in smooth air at low altitude with anticipated separation… A similar report was filed by a First Officer of a North Atlantic flight, whose descending aircraft may have caused a wake vortex problem for a climbing B-767:
The Case of the Phantom Load
ASRS recently received several flight crew reports of interest describing a widebody jet that thought it was airborne – while still on the ground. More details from the First Officer’s report:
s We were scheduled to fly a charter flight… We eventually
arrived at the aircraft [in early morning hours]. I performed the external aircraft preflight. When we approached the aircraft, the freight was in the process of being off-loaded from the main cargo deck. It was noted that there was no nosewheel strap or weight to hold the nose down. The Captain asked the load-master about this and was told there were none available and [he] assured us there would be no problem. We were expecting no freight in the upper cargo deck and very little in the forward belly. The preflight was normal. All doors were closed except for the main cargo door and left main cabin door (L1). We began the cockpit setup. All was normal until the main cargo door was closed. As it closed, numerous alerts came on. Neither of us had seen anything like this before. We called our maintenance personnel onboard. After removing power and resetting the aircraft, they restored everything to normal operation. I went back to close the L1 door. When I got back
to the cockpit, all the alerts had reappeared. We had maintenance come back onboard. They tried removing power again, but when it was reapplied, the stick-shakers activated. It was then that someone said it appeared the aircraft thought it was airborne. This did account for the alerts. Then one of the support people helping with the launch said that the nose strut was extended too far. He had experience with Air Force KC-10’s and said they couldn’t launch one with that much strut exposed. I went down and confirmed this. We realized that the Center of Gravity was too far aft. It was discovered that there were containers in A7 and A6, the most aft belly positions. The weight and balance showed an empty aircraft except for containers in F1 and F2, the most forward belly positions, weighing approximately 6300 pounds. At this point the…Captain directed [the load master] to reweigh the containers and load them in the proper positions. A new weight and balance form was brought to the aircraft and we then departed uneventfully.
ASRS Recently Issued Alerts On…
CL-65 inflight windshield failure A-300 uncommanded rudder movement at FL350 Mechanics’ misinterpretation of Piper gear kit instructions A runway signage problem at a major East Coast airport RB211 engine spinner fairing cracks found on two B-757s
A Monthly Safety Bulletin from
The Office of the NASA Aviation Safety Reporting System, P.O. Box 189, Moffett Field, CA 94035-0189 http://asrs.arc.nasa.gov/
September 2000 Report Intake
Air Carrier / Air Taxi Pilots General Aviation Pilots Controllers Cabin/Mechanics/Military/Other TOTAL 2236 623 106 183 3148
飞行翻译公司 www.aviation.cn 本文链接地址：美国ASRS安全公告CALLBACK cb_255.pdf
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