RC-47 Inflight Electrical Fire & System Failure!
By: —Chuck Miller, Lt. Col. USAF (Ret)
av8or@eos.net
We departed on the ferry flight from the eastern U.S. seaboard (N.H.)
with a destination in Vietnam in mid-January 1967.
Our itinerary was to proceed across the U.S. to McChord AFB
in Spokane, Washington, then north to Elmendorf AFB, (Anchorage) Alaska.
From there we proceeded southwest down the Aleutian Islands for 1000 n.m.
to Adak Island, navigating over the frigid Bering Sea.
Then 1400 n.m. south to Midway and island hopping on across
the Pacific to our destination.
The weather on departure from Elmendorf was typical winter
scattered-to-broken clouds with bases at about 3000 ft and tops about
7000 ft., so we had filed IFR at 8000 ft. and were initially on top in
clear sunny skies with a broken-to-solid undercast. The mission had a
flight plan duration of slightly over nine hours against a prevailing
headwind and a planned arrival after dark in the short arctic days of
late January.
Arrival weather was forecast to also be typical arctic island conditions with ceilings
and visibility near IFR minimums in blowing snow and winter sea fog.
The runway at Adak lay at near sea level in a valley surrounded by mountainous foothills
at elevations to about 1000 or 1500 feet, which when combined with
variable ocean winds caused turbulence and difficult radar approaches.
About five hours out of Elmendorf, I was hand-flying (no auto-pilot in these aircraft)
from the left seat, and I detected an odor resembling burning cellophane.
I asked my smoking co-pilot, 2nd Lt. Dave Dollahite,
if he had inadvertently set some cigarette pack materials on fire in his ashtray.
He responded in the negative.
I turned and glanced over my right shoulder into the aft of the aircraft to discover
the aft portion of the cabin rapidly filling with smoke.
Out of the corner of my eye, a red light caught my attention in the center of the
electrical control panel, which was on the bulkhead just behind the
cockpit emergency exit door, about 24 inches behind the bulkhead that
separated the pilot’s seats from the aft cabin and radio equipment
racks. A closer look revealed that this light was labeled
“”.
With what seemed like an impossible contortion, I managed to reach
around my seat back and associated bulkhead, and flipped the A.C. Main
Inverter switch to “Off”.
With that action, I suddenly found myself
with all the gyro instruments showing “Off Flags”, my electrical compass
system disabled, all navigation equipment off-line, and all but our
limited range primary UHF transceiver disabled.
As described in the “Project Phyllis Ann” link, the RC-47
(later redesignated EC-47) was an all-electric instrumented aircraft —
all the vacuum gyros and
systems had been deleted and replaced with sophisticated
(for that period) A.C. electrical powered equipment.
In the meantime, our Flight Mechanic, SSgt. James Gavin, donned the
smoke mask and hustled aft to the latrine in the tail
(where the inverters were located) with fire extinguisher in hand.
The fire was quickly extinguished with the inverter turned off, but it took over 30
minutes for the smoke to clear and an initial assessment of fire and
wiring damage to be made. The source of the fire proved to be the D.C.
motor on the main inverter, which had apparently overheated and burst into flames,
even though it was still successfully driving the integrated A.C. alternator.
Adding to our concern, however, was the fact
that the system design engineers had equipped the aircraft with an
“Alternate Inverter” of matching size and specification as the “Main
Inverter”, but had mounted it immediately above the Main and had used a
common electrical cable buss forward to the Electrical Control Panel.
This raised the potential that the Alternate Inverter, the buss control
relay and/or the common buss cable might have been damaged by the flames
and high temperatures caused by the failure of the Main Inverter.
For the next half hour, we were obligated to maintain heading and
attitude with “needle, ball, and airspeed” aided by the “whiskey
compass”, while contemplating our possible options. We had already
passed the “point of no return” fuel state for returning to Elmendorf.
The thought of having to make a “no-gyro” approach into Adak’s hilly
terrain at night, in IFR minimum conditions and in turbulence didn’t
sound too inviting,
but the thought of possibly ditching into the Bering
Sea with limited arctic survival equipment and no radio contact was even
less exciting to contemplate.
After the seeming interminable half hour passed and the damage assessment was completed,
the Sgt. Gavin suggested that we attempt to activate the Alternate Inverter to see if it would
pick up the load.
Fortunately, it came on line and worked fine for the duration of the flight!
Contents:
Home Page
Feedback