MolaKule
Staff member
quote:
Pinnacle Probe Unveils Training, Engine Flaws
Aviation Week & Space Technology 06/20/05
author: Frances Fiorino
Pinnacle Probe
Finding the cause of an accident often leads to a cure--and the ongoing probe of Pinnacle Airlines Flight 3701 is highlighting the need for enhanced high-altitude training and safety management programs at regional airlines.
Those shortcomings came to the fore during the NTSB's June 13-15 hearing that aimed to gather more information about the events leading to the Oct. 14, 2004, crash of a Bombardier CL600-2B19 (a.k.a. CRJ200) regional jet that resulted in the deaths of the two pilots on board. The board's findings show that on that date Pinnacle Airlines Flight 3701, operating as Northwest Airlink, departed Little Rock, Ark., at 9:21 p.m. local time on a repositioning flight to Minneapolis-St. Paul.
The flight plan showed an intended cruise altitude of 33,000 ft. or FL330, but at 9:43 p.m. the crew requested a climb to 41,000 ft., the service ceiling for the aircraft, and maintained that altitude for about 3.5 min. prior to stickshaker. About 20 sec. later, the aircraft was in a 32-deg. nose-down pitch and 80-deg. left bank. In that time period, the stickshaker and stick pusher had been activated four times. FDR data indicated both General Electric CF34-3B1 engines stopped simultaneously at 41,000 ft.
THE CREW DECLARED an emergency at 9:55 p.m., and 4 min. later requested descent to 13,000 ft. At 10:03 the crew informed ATC of a double-engine failure and requested vectors to the nearest airport; they were directed to Jefferson City (Mo.) airport. The crew reported runway approach end in sight, and at 10:15 p.m. the aircraft impacted the ground and was totally destroyed.
The captain had accumulated 6,900 hr. total flight time; the first officer, 761.
NTSB findings show that the crew attempted restarts according to manufacturer and company guidelines. However, the attempts were unsuccessful.
"If just one of the two stalled engines had restarted, this accident would never have occurred," said ALPA Chairman of Safety Terry McVenes. "The crew followed proper procedures. . . .But both engines failed to start because they had suffered "core lock--a risk previously known only to engine and aircraft manufacturers."
The engine core lock phenomenon is not well-known or understood throughout industry. The term refers to the seizure of the engine's core, or inner spool, by differential cooling that causes parts to bind.
Bombardier said every "prone" aircraft (CL300, CL604, CRJ200, DHC-08) is tested prior to delivery. During initial aircraft certification, engines are forced to 0% core speed and the aircraft is accelerated to confirm that engines will not lock up and can be windmill-restarted.
The manufacturer said the CF34-3 engine series has two areas suspected of causing core lock-up: the outer balance piston seal and inter-stage seal. The latter was found to be a contributor and a design change was implemented, reducing the lock-up phenomenon to 1.5%.
The NTSB Operations Group Factual Report revealed details about Pinnacle's training program, including:
*Jet upset training consisted of 6 hr. of ground school and 20 min. of simulator training at FL350.
*High-altitude climbs and recommended climb profiles were neither conducted nor demonstrated during simulator training--but were discussed at pre- and post-flight briefings.
*Double-engine failure training scenarios were not provided to pilots during simulator training.
*Operations at 41,000 ft. were not discussed or demonstrated in any ground or similar training segment--but the CRJ service ceiling was discussed in ground school.
Further, investigators learned there was a "sense of allure" to some pilots to cruise at FL410 just to say they had "been there, done that."
Several safety improvements have been implemented since the Flight 3701 accident: Pinnacle placed a 37,000-ft. ceiling on CL600-2B19s and issued an alert bulletin telling flight crews to no longer accept or request clearances above FL370. Simulator training now includes high-altitude stall and stall buffet margin demonstrations. The airline also revised the instructor's guide to include single- and double-engine failures at 35,000 ft. in initial new-hire and captain upgrade training.
BOMBARDIER ON MAY 16 published a revised Airplane Flight Manual procedure for dual-engine failure aimed at improving chances of recovery. The FAA on June 2 issued a Special Airworthiness Information Bulletin instructing pilots on how to avoid the dangers of core lock.
The main training concern, according to ALPA, centers on low-time pilots shifting to jet operations too early, or pilots not gaining thorough training in high-altitude operations.
"The regionals are undergoing enormous growth and adding more sophisticated aircraft to fleets. The environment means pilots have less time to gain first-hand experience with aircraft before assuming command," says McVenes, who emphasized he is discussing regional carriers in general. "Regional carriers over the last few years have been transitioning from turboprop equipment, which typically fly below 25,000 ft. and in a slower [airspeed] regime where things just don't happen that fast," explains McVenes. He points out that aerodynamics differ between turboprop and high-performance jets, and that pilots need to recognize those important differences.
In contrast, he notes, pilots training at legacy carriers get a "big block" of high-altitude operations training.
Pinnacle said at the hearing that it intends to implement a Flight Operational Quality Assurance program, which will aid in detecting and correcting potential safety problems. The NTSB investigation of Flight 3701 is ongoing, and NTSB member Deborah Hersman, who chaired the three-day hearing, says the final report is not expected to be completed until late this year.
