Sep 2016 F-35A engine fire sparked by strong tail winds

[SpudmanWP]

WASHINGTON — U.S. Air Force investigators have found that last September’s F-35A mishap at Mountain Home Air Force Base, Idaho, was indeed an uncontained engine fire — albeit one started because of tailwinds present during engine start, not deficiencies with the aircraft’s Pratt and Whitney F135 engine.

According to a U.S. Air Force accident investigation board, or AIB, report signed May 9 by the board’s president and obtained by Defense News, the engine fire started after tailwinds forced hot air into the inlet of the jet’s integrated power pack. A chain of factors, such as insufficient torque and slow engine rotation speed, caused the F-35 to continuously supply fuel to its engine at an increased rate.

“During this mishap, however, the fire became uncontained due to the increased amount of fuel added while the engine rotation speed was slowing,” the report stated. “Once the uncontained fire started coming out of the aircraft exhaust, the tailwind carried it rapidly along the exterior surfaces of the jet.”

The pilot escaped from the aircraft but sustained burns to his head, neck and face.

The service is still evaluating how much it will cost to repair the F-35A involved in the mishap, which was assigned to the 61st Fighter Squadron at Luke Air Force Base, Arizona, and involved in a training flight at Mountain Home when the fire occurred. However, damage to the plane is estimated to amount to at least $17 million.

Ultimately, the mishap had little effect on F-35 training and operations. After the fire broke out on Sept. 23, the U.S. Air Force announced that it had no plans of grounding its F-35As — a sign that the service believed the incident arose because of weather or human factors rather than a design flaw. The F-35 joint program executive office has not announced modifications to the jet as a result of the event.

The AIB report noted that aircraft systems, including the F135 engine, performed as designed. Still, investigators stated that more could have been done to prevent the mishap, especially in the realm of educating pilots.

For instance, the service did not include information about how tailwinds contribute to integrated power pack failures on its engine start checklist. Pilots were also not given any additional training on concerns related to tailwinds and were not aware of warning signs that the F-35 exhibits when tailwinds cause issues with the jet’s power and propulsion systems.

“[Integrated power pack] and engine start issues with a tailwind were known prior to the incident. However, the publications were written and communicated in such a way that the F-35A pilot community had only vague awareness of the issue. This vague awareness led to inadequate training for engine starts with a tailwind,” Col. Dale Hetke, the AIB’s president, wrote in his statement of opinion on the investigation.

The F-35 is renowned for its complex software and sensor fusion capabilities, but Hetke noted that the level of automation present in the aircraft led to some complacency within the pilot community.

“The F-35A engine start process is heavily automated, which drove a perception among pilots [that] the aircraft handled virtually all of the starting procedures, and so long as the dials were ‘green’ there was no problems,” the AIB report stated.

During the incident, the fire spread along about two-thirds of the aircraft’s aft surfaces, with most burn damage occurring on the top, side and underneath portion in the center of the jet, the report said.

Because the aircraft’s weapon bay doors are open during engine start, the fire spread to aircraft surfaces, panels, cables and components. The aircraft’s landing gear was damaged, and its integrated power pack will need to be replaced.

Investigators noted that the engine’s exhaust nozzle section was engulfed in flames but did not spell out how much of the engine will need to be repaired or replaced.

http://www.defensenews.com/articles/f-3 ... -tailwinds

[blindpilot]

WASHINGTON — U.S. Air Force investigators ...
The service is still evaluating how much it will cost to repair the F-35A involved in the mishap, which was assigned to the 61st Fighter Squadron at Luke Air Force Base, Arizona, and involved in a training flight at Mountain Home when the fire occurred. However, damage to the plane is estimated to amount to at least $17 million.
..

http://www.defensenews.com/articles/f-3 ... -tailwinds

Just give it to the Israelis. They can attach the tail end of an old F-16 crash and turn it into an F-22 ...
( http://jewishbusinessnews.com/2017/05/1 ... loss-f-15/ )

BP

[maus92]

I guess they need to install windsocks on GSE. What was the windspeed anyway? I haven't seen that pasted anywhere yet. Also wasn't aware of the pilot being injured. The amount / cost of the damage isn't surprising - 2/3 of the center fuselage skin being damaged, and the open bay / gear doors.

[neptune]

https://www.flightglobal.com/news/artic ... ds-439269/


USAF pins F-35A engine fire on strong tailwinds


BY: Leigh Giangreco
12 July, 2017


A US Air Force investigation blames a Lockheed Martin F-35A engine fire last September at Mountain Home AFB, Idaho, on strong tailwinds, according to an accident report released by the service this week. Winds as high as 30kt blew during as the Pratt & Whitney F135 engine began a start sequence, forcing hot air into the Honeywell integrated power package's inlet. As air temperatures rose inside the IPP -- a mini-engine that supplies electric power and starts the engine -- a series of malfunctions occurred. The lower density of the air produced insufficient torque needed to the engine, which slowed the rotation of the turbine section. At the same time, fuel continued to supply the engine at an increasing rate, which spurred an engine fire that burst from the exhaust. The tailwind spread the fire across the aircraft and caused significant damage to a portion of aircraft’s aft section. The fire surrounded the engine’s exhaust nozzle, damaging several nozzle segments as well.

The pilot escaped but sustained minor injuries, including burns on his head, neck, face, and ears, the report states. The service has not yet determined the total costs, but estimates aircraft damages will cost above $17 million. (Class A??)

The report also lays blame on a lack of pilot awareness and training for tailwind conditions during an engine start. A pilot checklist included a warning that strong tailwinds during an engine’s start could cause an IPP failure, but the checklist made no warnings about the tailwind limit. The heavily automated F-35A engine start process also led pilots to believe the aircraft handled most of the start procedures and pilots assumed there were no problems if the dials were green, according to the report. “Preponderance of evidence shows if there had been an expectation of engine startup problems with a tailwind, the [pilot] may have relied less on aircraft automation, and may have identified an abnormal engine start earlier,” writes USAF Colonel Dale Hetke, who conducted the investigation. “This vague awareness led to inadequate training for engine starts with a tailwind. Training also resulted in complacency and an over-reliance on aircraft automation.”


....beats the heck out of all the "hot starts" I've had or seen, (no damages/ or noticeable), different world now!

[35_aoa]

Have seen this in F404/F414/F100's too, though to a seemingly lesser degree. Not as impressive as the tailpipe fireball a 404 will give you on a real cold high alt morning (Fallon) if not motored long enough to increase EGT. Wingman did it and being parked next to him with the canopy up, I still felt the heat.......and the 50 foot long fireball behind his jet. Apples to oranges, but environmentals can be a cause of various start anomalies.

[spazsinbad]

Tailwind Caused September F-35 Engine Fire
13 Jul 2017 Brian Everstine and John A. Tirpak

"A strong tailwind caused the engine of an F-35A to catch fire last fall, prompting checklist revisions and new precautions and procedures to be put in place to change how F-35s are handled on the ground....

...The fire came out of the engine exhaust, with the tail wind carrying it along outer surfaces of the jet. This caused extensive damage before being extinguished about 20 seconds after the first visual indications of the fire, the report states. The jet, tail number 12-5052, was deployed to Mountain Home from Luke AFB, Ariz., and was preparing for a training flight....

...Because the fire spread with speed, the pilot had trouble following the checklist. For example, the pilot did not move the engine switch to “off” in accordance with the egress checklist. Within seconds, the fire reached the landing gear.

“It stands to reason that if the engine switch had been moved to off at the first indication of fire, fuel would have been shut off to the engine nearly immediately and the fire would not have burned as long,” the report states. The pilot was under duress, however, and sustained burns to his head, neck, face, and ears.

Following the AIB report, AETC implemented procedural fixes and checklist changes to prevent similar mishaps, including a 20-knot tailwind limit for the start of an F-35 engine...."

Graphic: http://www.airforcemag.com/Features/Pub ... .05_pm.png

REPORT: http://www.airforcemag.com/AircraftAcci ... INHOME.pdf (1.4Mb)

Source: http://www.airforcemag.com/Features/Pag ... -Fire.aspx

[krorvik]

Besides the technical reasoning - this is a textbook case of automation reducing pilot awareness to procedural details - or even (own) existing experience.

[sferrin]

"F-35s can't fly on windy days." - Basement Dweller Crowd

[spazsinbad]

Attached PDF of one page just repeats what is in the accident report with JPG shown from Airforce Monthly Mag Sep 2017.

[That_Engine_Guy]

Not supposed to start jets with high tail winds.

Every one I've ever worked have a maximum tailwind start requirement in technical data. Even during trim runs the winds needed to be below a specific threshold or within so many degrees of the nose.

This sounds procedural, not technical.

Note; you can't start them under water either (not in the books, but good tip from TEG)

Keep 'em flyin'
TEG

[spazsinbad]

Do they work in OUTER SPACE - the TWILIGHT ZONE?!

[cavok]

Mishappening... Happened to many types while igniting during "limit" conditions. I'm far more concerned with rubbing issue (imho "too tight" clearances causing excess rubbing is not a "root" cause as it only happened after high g manoeuvers, root cause is to be assessed somewhere into the effect of theses high g manoeuvres which should NOT have resuted in excessive rubbing)

[neptune]

Mishappening... Happened to many types while igniting during "limit" conditions. I'm far more concerned with rubbing issue (imho "too tight" clearances causing excess rubbing is not a "root" cause as it only happened after high g manoeuvers, root cause is to be assessed somewhere into the effect of theses high g manoeuvres which should NOT have resuted in excessive rubbing)

...tight clearances in turbine driven compressors is a known limitation. In the compressor end, abradable seals are "worn-in" by a designed time and power schedule. I will defer to TEG for the specifics on the existing jet engines.

That said, PW has an extensive knowledge base and the development of the F-135 at the time of the incident knew/ published exactly the limitations for that time on that engine. Unfortunately the engine monitoring system was not "connected/ talking to ALIS, at that time (since connected). That monitoring system does alarm the pilot when the accelerometers detect the excessive vibrations on the rotor, sadly not for the "brake-in" period for that a/c. IMHO, a not so diligent "hot rod" exceeded the published limitations (at the time) and got away with the rubbing until that fateful morning of the run-up for takeoff. In my experience mechanical systems rarely fix themselves after they have been abused.

[cavok]

Thank you Neptune for deep insignt info. Very interesting and makes sense.

[spazsinbad]

I saw a claim that this aircraft was 'written off' however have only found this/these same articles - apologies if repeat.

Gunfighters complete first F-35 transport [Photos at URL - I thought USMC or others have carried out a lift?]
15 Nov 2017 Senior Airman Malissa Armstrong, 366th Fighter Wing Public Affairs

"MOUNTAIN HOME AIR FORCE BASE, Idaho --
An F-35A Lightning II belonging to Luke AFB, Ariz. was moved for repairs after being grounded here for the past year. The aircraft was moved to the F-35 Depot at Hill AFB, Utah, with the help of the 366th Equipment Maintenance Squadron crash and recovery team....

...Previously, a lift like this was only performed by the engineers at Lockheed Martin. “366th Crash Recovery (an F-15 unit) was the first to do an actual lift on an F-35,” said Daniel Santos, 809th Depot manager at Hill AFB. “What's even more remarkable is Mitchell and his crew have no F-35 experience (or) training and using F-35 tech data, they performed a flawless lift.”

The main concern was getting the aircraft to Hill’s F-35 depot with no more damage than it already sustained. According to Fox, the ultimate goal is to get it back to mission ready or use its parts in other aircrafts.…"

Source: https://www.mountainhome.af.mil/News/Ar ... transport/