Aviation Safety Digest
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G.\.C ~. , ....... Commonwealth of Australia I AVIATION SAFETY DIGEST ......• J No. 12 DECEMBER, 1957 Printed by Hedges & Bell Ply. Ltd , Moryborough, Vic. Aviation Safety News and Views Digest No. 12 - December, 1957 Flight Instruments and Electrical Power CONTENTS Failure Warning Page ( Reproduced from Pilots' Safety Exchange Bulletin 57-104 issued by the News and Views Flight Sa/et'' Foundation, N ew York, U.S.A.) Flight Instruments · and Electrical A recent investigation of an air Power Failure Warning C.A.A. aviation safety agent, a transport accident involving a "sud C.A.B. electrical systems specialist Collisions with Overhead W ires 4 and three airline captains. A Lesson Learnt . 6 den and surprising" crash landing almost immediately after take-off, Following are the facts of their disclosed inadequacies in the present report - Overseas Accidents day electrical power failure warn Crash following Missed Approach - ing system. particularly as it affects At Lhe beginning of the tests, the Douglas DC.6B - Cold Bay, Alaska 7 flight instnunents. While actual in aircraft was parked with engines off Mortin 404 Strikes Mountain - ftight instrument failures are not and d.c. power supplied by a ground Albuquerque, New Mexico . B commonplace, they have happened power unit. The d.c. bus voltage I LS Approach Accident al Blockbushe 10 and have been attested to by highly was measured to be 28 volts. Mag- Martin 404 - Los Vegas, Nevada 1 2 qualified and experienced pilots. 11etic compass heading read 170°. Dove Accident - New Forest Hamp· For example, while on an ILS Captain's and first officer's Collins shire, England 14 approach. the captain of a twin Course Indic::itor compass cards DC.4 En-route Collision with Terrain 15 enginc transport reported his horizon read 175°. slowly indicated a bank. The first Main inverters were turned on. Australian Accidents officer, who was flying the plane Captain's selector switch was placed from the left seat, tried to keep the in 'Up' position; engine instnunent DC.4 Damaged in Undershoot 17 airplane in relation to what the selector switch was in 'Up'; first Procrastinotian in a DH.B2 1 8 horizon was telling him. The horizon officer's selector switch was in Agricultural DH.82 Strikes Fence dur- on the right side, however, was in ·Down' position. Output voltage of ing Take-off . 1 9 dicating just the reverse, so the cap each inverter was measured to be tain corrected the manoeuvre. In That Check for Water Needs Careful 115 volts a.c.: freq1wncy 410 c.p.s. Thought 19 vcstiga tion subsequently disclosed Agricultural DH.B2 Collides with that the horizon on the left side had Electricity Wires 21 failed with no warning light indica Compass Card Reaction Fatal Accident in Authorized Low tion. The trouble was found to be As inverters were turned on, com Flying . 22 in the Phase C circuit - the l 15V pass cards of the' two Collins CouJ"se Agricultural DH.82 Collides with High Phase Circuit breaker had popped Tension Power Cables 22 rndicators were watched closely. out. This incident proves a point Neither changed position. Slaving that may not be well known to any knob of captain's C-2 gyrosyn was one except electronics specialists. Incidents rotaled lo displace the dial. Cap namely, that the inverter failure tain's course indicator compass carci It Would Have Been Much Closer warning lights may not give warning slaved to C-2. while first officer's in Cloud 24 where there is loss of only one co11rse indicator card was 11naffected. A Lively Spork 25 phase of AC power. Rudder Control Cable Failure 26 After turning on inve1·ters, time Too Close 26 Jn the light (or lack of it) of this for gyro horizons to erect were: 111ost recent experience, the results captain's horizon - 8 seconds; fi rsl Design Notes of electrical tests performed on a officer's hori7on - 3 minutes. sister-ship of the one involved in Stabilizer Actuator 28 the crash landing may be of interest, Phase A-Upper Inverter particularly 10 those who operate aircraft employing only electrical After allowing the gyros time to (Prepared by Division of Accident Investiga fl ight instruments. reach operating speed. Phase A cir tion and Anaysis. Published by authority of cuit breaker of 11ppC'r inverter was Director-General.) Those doing the tests included a opened: 1· the Sf'<:ondary voltage was 22.9 volts. and aircraft was taxied to new I. Captain's inverter warning light cuiL breaker ·of lower inverter was Captain's Instrument Transformer reach operating speed, the Phase A did not light. opened: T he gyro horizon had not yet tum location for further tests. As air circuit breaker of the upper inverter Fuse in Phase A of primary of the bled. craft heading changed, compass was opened. Forty seconds later the 2. Captain's gyro horizon tumbled 1. First officer's inverter warning captain's instrument transfo rmer was A check was made to determine card of first officer's course in aircraft was taxied straight ahead. 2 minutes later. Bar moved up light did not come on. removed. T he captain's inverter what effect the C-2 g}'rosyn would dicator rotated and indicated new The gyro tumbled l minute, 10 sec and to the left, then over to the warning light did not come on a l li avc on the secondary voltage when headings in agreement with cap onds after the circuit breake1· was right. C-2 gyrosyn slaving knob 2. First officer's gyro horizon tum once. However, it did come on 5 Phase A circuit breaker was opened. tain's course indicator compass card. opened. The horizon bar' Li lted to was turned and captain's course bled 2 minutes la ter. The hori minutes later while the group waited Fuses to the C-2 were removed and On same inverter switch selection, the left. The captain's inverter warn indicator compass card followed zon bar lowered with slight til t fo r .t,'yro horizon to tumble. rhc test repeated wherein Phase A Phase A circuit breaker of upper ing light did not come on. The cir gyrosyn card. to left, then raised with slight circuit breaker was opened. No dif inverter was opened. Engine instru cuit breaker was then closed. The Phase A fuse was replaced after tilt to right. I t reached top and ference in seconda ry voltage was ment operation remained normal testing was concluded at this point. 3. Cabin pressure control could not allowing gyros to reach operating rested in level attitude. When noted. The voltage increased from 26 and captain's inverter warning fail be checked while unpressurised. speed ; P hase C fuse of primary side Until answers are found to the instrument was tapped by hand, volts to 29 and remained there. ure light remained off. Fuel quanti of same transformer was pulled. question of reliable performance of 4. F uel quantity: no reading. bar fell off to left. \'\lith same inverter selection, ty indication ceased. A hard right Captain's inverter warning light electrical flight instruments, ade Phase A and Phase B circuit breakers Lurn of 360° was made and only a 5. Engine Analyser: not installed. '.l. Pedestal lights stayed on. came on immediately. quate warning of power or in of upper inverter were individually one-half needle width turn was indi strwnent failure, etc., it would 6. Zero Reader: Vertical main 4. Power to A-12 gyro pilot was off. Fuse was replaced. Following a opened. Check was made Lo sec if cated by the captain's turn and appear that an alternate means of pointer of the indicator and With aircraft a t rest, slaving of similar procedure, Phase A and C:-2 would slave to flu x \'alves : with bank indicator. T he gyro horizon flight instrumentation is desirable. heading arrow of heading selec co-pilot's course indicator card Phase C fuses of secondary side of either circuit breaker open, there was tumbled after 1 m inute and 45 sec For example, an air-driven flight tor slaved with C-2. When lo A-12 gyrosyn compass could transformer were individually re no slaving action. Slaving of verti onds with the horizon bar falling group or non-electrically operated heading selector setting was not be checked. moved. In each case the warning cal main pointer of Zero Reader in and tilting to the left. At this time gyro instruments for primary use changed, vertical main pointer ligh l came on as soon as fuse was dica tor was checked. When Phase A it was noted that the C-2 operated rather than utilizing only electricaJ'fy responded. 5. Radio Altimeter: nut installed. removed. circuit breaker was opened, it slaved only as a directional gyro. It was driven instruments. lo C-2 gyrosyn. When Phase C cir not slaving to its flux valves. 7. VOR No. 1: went off. 6. Loran: not installed. All instruments were then operated cuit breaker was opened, it did not from the upper inverter and its cir The Phase A circuit breaker of the Comment 8. VHF No. 1: went off. 7. ADF No. 2 : R eceiver was off ~l ave . Phase A and P hase C fuses of cuit breakers individually opened to first offi cer's instrument transformer upper inverter was closed. T he Phase and indicator was inoperative. A and Phase C fuses of the Zero Most power failure warning sys 9. Glicleslope No. 1 : went off. observe the beha,-iour of the inverter ~econdary were individually removed tems sense a loss of power at the 8.