Airforces

ATTRITION

Subscribe to http://www.airforcesmonthly.com

for breaking news stories. E-mail the news

team at [email protected]

Strong tailwind caused

F-35A engine fire

A STRONG tailwind has been

confirmed as the cause of

the engine fire that seriously

damaged a US Air Force F-35A

Lightning II during start-up at

Mountain Home Air Force Base,

Idaho, on September 23, 2016,

see Attrition, November 2016,

p92. An Air Education and

Training Command (AETC) Aircraft

Accident Investigation Report

into the incident was released on

July 12. It identifies the aircraft

as 12-5052, assigned to the 61st

Fighter Squadron ‘Top Dogs’,

from the 56th Fighter Wing at

Luke Air Force Base, Arizona.

The aircraft was temporarily

deployed to Mountain Home

along with six other F-35As from

September 10-24 for training.

At approximately 0852hrs

the aircraft experienced an

uncontained engine fire during

start. The start-up was aborted

and the pilot safely egressed

the still-burning aircraft,

suffering only minor burns to

his head. Maintenance crew

members responded and

extinguished the fire. The rear

portion of the aircraft sustained

significant fire damage. The

report says that while total

costs resulting from this mishap

have still to be determined,

damage is estimated to

be in excess of $17m.

The Accident Investigation

Board (AIB) President found, by a

preponderance of the evidence,

that the cause of the mishap

was the direct tailwind present

during engine start. Wind

sensors on the airfield indicate

that a wind speed of 30kts or

greater was present during this

process. This forced hot air into

the inlet of the Integrated Power

Pack (IPP), which led to a series

of events resulting in insufficient

torque applied to the aircraft

engine during start, causing

rotation speed to slow. At the

same time, fuel continued to

be supplied to the engine at an

increasing rate, which triggered

an uncontained fire in the

unit. This spread out from the

engine exhaust and was carried

along the outer surfaces of the

aircraft by the tailwind, causing

significant damage. The fire

was extinguished approximately

20 seconds after initial visual

indications of the problem.

The fire damaged the engine

exhaust nozzle, landing gear

surfaces and components in

both the left and right main

undercarriage wheel wells. As

both weapon bay doors were

open, flames penetrated both

bays. The outer surface of the

aircraft on the aft two thirds of

the airframe’s centre fuselage

suffered varying degrees of

damage. Some minor damage

was even noted on surfaces

forward of the cockpit.

The report notes that neither

publications nor training were

adequate for the circumstances

surrounding this incident. IPP

and engine start issues with a

tailwind were known prior to this

incident, however, publications

were written and communicated

in such a way that the F-35A

pilot community only had a

vague awareness of the potential

issue. Evidence shows that if

the pilot had expected problems

with the tailwind, he may have

relied less on automation and

identified the abnormal start-

up earlier. The fire’s ferocity

and close proximity impaired

the pilot’s ability to follow the

checklist. In the necessary haste

to exit the burning aircraft,

he failed to move the engine

switch to off, in accordance with

the egress checklist, before

leaving the cockpit. Had he

done so at the first indication

of fire, fuel would have been

shut off from the engine almost

immediately and the fire would

not have been so fierce. The

report accepts, however, that

prioritising egress was necessary

due to the imminent danger.

Procedural guidance,

publications and checklist

error were thus determined

to be substantial contributing

factors to the overall extent

of damage. AETC stated that

fixes and checklist revisions

have already been put into

place to prevent further

such incidents. This includes

implementing a maximum 20kt

tailwind limit for engine start

on the F-35 and adding more

robust engine start and pilot

emergency departure training.

Above: The upper rear fuselage of F-35A 12-5052 following its engine fire on September 23, 2016, at Mountain Home AFB. USAF

88 // SEPTEMBER 2017 #354 http://www.airforcesmonthly.com