*' employee bulletin - boeing ch-47...
TRANSCRIPT
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*' EMPLOYEE BULLETIN
No. 75-38 November 25, 1975
UTTAS 001 ACCIDENT SEQUENCE ESTABLISHEDAIRCRAFT REPAIRABLE
The sequence of events in UTTAS aircraft 001 accident have been clearly established. During buildup maneuvers toward the 85 knot autorotative pull-out point of the structural demonstration an RPM overshoot to approximately 125% of normal RPM was encountered. During the RPM overshoot the most forward section of the tail rotor drive shafting (between the main transmission and the intermediate transmission) contacted a work step in the aft transmission compartment. The contact with this step tore the first section of shaft causing it to fail and eliminating the drive torque to the tailrotor. This, of course, resulted in the loss of directional control. Due to the low airspeed and low altitude existing following this occurrence, it was impossible to get the aircraft into a forward flight speed regime where adequate vertical tail effectiveness would provide directional control of the aircraft. The aircraft came down into a patch of dense oak woods.
Accident Investigation Board
The U. S. Army has established an official military accident investigation board headed by Colonel Dennis Boyle to investigate the accident. The Company is cooperating fully with the Board. Any official public releases will be made by the Army Board.
UTTAS aircraft 002 and 003 have been cleared by the Army to resume their flight test program. Also, the Army's Pilot Evaluation Program is proceeding as planned, operating with autorotative RPM restrictions which will avoid the recurrence of the 001 problem.
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001 Repairable
On Saturday, November 22, a CH-47 Chinook piloted by A. J. Hutto and Al Santa Maria airlifted the UTTAS aircraft from the crash site to the company's facility at the Calverton, Long Island test center. Today, 001 is being brought back to Center 3 at Boeing Center.
Since shortly after the accident took place, a team from Boeing Vertol has been "on the scene" determining the extent of damage to the aircraft.
The main fuselage structure is essentially undamaged. The tail rotor has four blades still attached to the straps in proper connection to the tail rotor hub and shaft even though the tail boom broke loose from the aircraft. Based upon detailed examinations of the damaged aircraft, the company is recommending to the U. S. Army that 001 be repaired and returned to flight status.
Impact on Program
We are reviewing the impact of the accident on our schedule for delivery of aircraft for the Government Competitive Test. A delay of approximately one month is currently indicated based on developing and qualifying an adequate fix for the tail rotor shaft and then completing the aircraft Structural Demonstration program.
Crashworthiness Demonstrated
Just as every dark cloud has its bright lining, this accident was a spectacular demonstration of the crashworthiness of the YUH-61 design. Both of our pilots, Frank Duke and Ron Mecklin, were uninjured and there was no fire.
During entry into the woods the main rotor blades and tail rotor blades contacted a number of oak trees ranging in diameter from 6" to 15". The transmission is firmly in place in the aircraft structure with no evidence of any movement of the transmission and transmission mounting structure. For example, it was possible to open the hatch immediately aft of the transmission with no evidence that any structural deformation of the butt line beams on which the hatch tracks are mounted had taken place.
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CH-47C Chinook, piloted by A. J. Hutto and Al Santa Maria, returns 001 UTTAS to Calverton flight test facility.
The following photographs taken at the Calverton test center on Saturday, November 22, show the structural integrity demonstrated by the rotor system and airframe structure.
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MISHAP REPORT i;; ~;-' II q 1 ~ '. ~ !
11/20/75 F. H. Duke
15.3"Ae.g •
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2 hours
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:= ACCIDENT~: .. ILANDING:, 'B'" SATL~~KA£-" • , of<~ 'B:,r,ill£';-~--;- ""-~;,\>-,;.,,,~{~~~p-.,,-,~NON-la"'-:. ,.., 0' ,"" lXl PRECAUT I ONERY RECOVERABLE _,._,., " , <~ ~;;:; L...JMAJOR ."4' ':"Fi i 0 FORCED ': MAJOR' , , =~ '0 I • SUBSTA""I;':' MilleR. :' NO DM~AGE EXPLOS'ION ':;--:~S~ISHAP ~ti INCIDENT j:=JCOMBAT DAMAGE i LIMITED 1--1 OTHER MISHAP
179
§OVERHAUL ROPERATION':' -'" OPERATION .j OPERATION !JDPERAT I ON
22 TOW I Nt'a f R£AR FLrGh~ ------------1---1 I 23 SL I NGiHO 1ST ",::>OK -UP16 GO AROUND~ SIDE FLIGhT
1- 24 SL I NG/HO/ST FrELEA:SE>;;'17 'ROTOP. SHUTDOWNtol CL 1MB
251 GROL'ND SERV I CE. ,,"18 ROT:JR FOLD111 GESCENT
2,6 GROUND OPER,>,TIONS19, L M,D <PPROACHI:: AUTORO: A 7 j :-::-;
20 PA'?!<ED -- GROUND 27 Cruise ,"',
: 28WATER I
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~~,Developed leak in #2 hydraulic boost system. Low quantity caution light was <:::0' ;~ followed by loss 'of oil pressurE7 and loss' of _#2 SAS.- 7 ~ "
DEW POINT '-"1 WIND .-' ',\lND DIRECTlON ,. ,. VELOCIT":C , .<jO. ,
Cd LING I,T EMP 0',c(F. l. , NW at 10,.. '-, 10 knotsNo'factor 2 7 '!;I," .......:.r'. :::.;.~-:. 12ia:.""':"'" ,,;.
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Aircraf,t landed at Salem Airport. Determined leak to be"'tail rotor : :, ,contro1 actuator. Isolated the #2 boost lines to the tail-'rotor "
and re-serviced the svstem and returned to Wilmington:": - ' ~- '- ~.1°'Li""----..~;'"II' 'j, .... ~ \ .... ~ ..._,- ....'!
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