Luke AFB sends 13 airmen to hospital over possible hydrazine exposure

[MechAg94]

Luke AFB sends 13 airmen to hospital over possible hydrazine exposure
https://taskandpurpose.com/news/luke-air-force-base-hazmat/?utm_term=Task%26Purpose_Today_08.28.24&utm_campaign=Task%20%26%20Purpose_TPToday_Actives_Dynamic&utm_source=Sailthru&utm_medium=email

The initial event involving the first ten airmen happened at 4:40 p.m. local time after an F-16’s EPU was somehow activated.

Response teams first shut down and cleared the area to investigate, and no hydrazine was detected. The response team terminated the ground emergency at approximately 5:22 p.m, base officials said. Approximately five hours later, the response team declared another ground emergency related to the same F-16 at about 9:45 p.m. Teams again confirmed no hydrazine release from the EPU, and the ground emergency was terminated.

Three more airmen were transported to local hospitals “out of an abundance of caution,” base officials said, after the second emergency.

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The F-16 has been taken off the flight line for further testing.

Hydrazine is a key propellant widely used in the military’s fighter jets and NASA and SpaceX’s shuttles and rockets. It is toxic, caustic, and a probable carcinogen to people and can be absorbed within seconds of contact with bare skin, inhalation, and ingestion. When absorbed through the skin, liquid hydrazine acts as a neurotoxin and can cause severe burns, seizures, and death.

I saw this headline.  I figured some of y'all would be able to tell me what we use hydrazine for?  This mentions the "EPU".  Is that "emergency power unit"?  Just curious about what it is used for and is that mixed in with the normal jet fuel or used separately?

[dogmush]

Diluted Hydrazine is used in some military jet's Emergency Power Units (yep that's what EPU means) because it does not require oxygen or ignition to work.  They stream the Hydrazine over a catalyst and it decomposes to steam (and other things) without any further input.

This let's the EPU turbines spin up *very* fast and provide the power (presumably during an emergency)  as quick as possible.

Using a small get and jet A to spin the turbine would take a lot longer, and outside power (battery starter or something)  to get going. I think the EPU hits full chooch in like 2 or 3 secs.

[Northwoods]

Apparently it's an Emergency Power Unit.  It uses hydrazine as a monopropellent.  It's meant to provide short term electrical and hydraulic energy.

[MechAg94]

Interesting.  Thanks.

[dogmush]

If you are interested, I found this while I was double checking what I thought I remembered:

https://aviation.stackexchange.com/questions/23417/why-is-hydrazine-used-to-power-the-f-16s-epu

The EPU of F-16 is fueled with a monopropellant hydrazine mixture, H-70, which contains 70% hydrazine (N2H4
) and 30% water, by weight.

The main requirements for the EPU are that it should be simple, maintenance free, supply power immediately and consistently for the required time. Use of Hydrazine assures this while requiring careful handling.

Basically, the catalytic decomposition of hydrazine produces ammonia, nitrogen and hydrogen. Exhuast Gases from EPU Turbine contain 40% Ammonia, 17% Nitrogen, 15% Hydrogen and 28% Water.

3N2H4→4NH3+N2
4NH3→2N2+6H2
3N2H4→4(1−x)NH3+6xH2+(2x+1)N2
where x is the fraction of the NH3
 disassociated.

The water modifies the decomposition temperature (the EPU reaches temperatures of ~870 ∘C
), preventing thermal damage to the catalyst bed and the turbine parts. As the water removes heat, it is turned into steam which aids in powering the EPU.

The EPU, using hydrazine spins up to approximately 75,000 rpm in 2-3 seconds (The F-16 EPU starts within 2 sec.). It would take a much greater time if another fuel, like JP-8 were used. When required (EPU runs normally on engine bleed air), hydrazine is forced into decomposition chamber by nitrogen pressure, where the above reactions produce the gases to run the turbine/gearbox. The decomposition of hydrazine produces enough pressure, eliminating the need for a compressor, thus saving weight and also eliminating the need for an igniter, reducing complexity.

For the given weight, it provides continuous operation for the required time. In F-16, the EPU carries ~25l of hydrazine, which permits operation for about 10 minutes under normal load conditions and 15 minutes if the loads are less (i.e. in ground). If any other form, (like battery or cartridge) were used, it would be difficult to have a long operational time without heavy increase in mass.

For a combat aircraft, RAT is not an option. Also, a hydrazine powered EPU would work in any altitude or during maneuvering as it does not need an external oxidizer supply.

References:

Exhaust Gas Composition of the F-16 Emergency Power Unit by Harry J. Suggs et al.

Technical Order 00-105E-9, USAF

AFR 110-14 USAF Aircraft Accident Investigation Report.

F-16 manual

[Brad Johnson]

Hydrazine is also used in spacecraft maneuvering thrusters.

Brad

[BobR]

Another monofuel that was used by the USN was Otto Fuel in the torpedoes, both surface, sub-surface and airborne delivered. It was one of those things that they said, if you smell it you really need to leave right now. In all of my time loading and carrying torps I can only recall one Otto fuel leak ad that was during a loading evolution.

If you go to page 4 of this document you can learn even more.

For a combat aircraft, RAT is not an option. Also, a hydrazine powered EPU would work in any altitude or during maneuvering as it does not need an external oxidizer supply.

That must be on the newer a heavier than air type of machines, I can recall the A6E, the F4B and F4J had them because I worked on them.


Otto fuel info. It is amazing the stuff the military uses that is known to be hazardous but back in the day we didn't even consider it when working around it. PPE? bah...never heard of it!

https://en.wikipedia.org/wiki/Otto_fuel_II


bob

[MechAg94]

Another monofuel that was used by the USN was Otto Fuel in the torpedoes, both surface, sub-surface and airborne delivered. It was one of those things that they said, if you smell it you really need to leave right now. In all of my time loading and carrying torps I can only recall one Otto fuel leak ad that was during a loading evolution.

If you go to page 4 of this document you can learn even more.

That must be on the newer a heavier than air type of machines, I can recall the A6E, the F4B and F4J had them because I worked on them.


Otto fuel info. It is amazing the stuff the military uses that is known to be hazardous but back in the day we didn't even consider it when working around it. PPE? bah...never heard of it!

https://en.wikipedia.org/wiki/Otto_fuel_II


bob

Chemical plants used to be the same way about a lot of stuff.  I have had people tell me they washed their hands in benzene and ear protection was a big wad of cotton near the door. 

[Hawkmoon]

For a combat aircraft, RAT is not an option. Also, a hydrazine powered EPU would work in any altitude or during maneuvering as it does not need an external oxidizer supply.

What is RAT?

[BobR]

What is RAT?

Ram Air Turbine.

A small air driven generator and hydraulic pump combo (usually) that is deployed into the airstream in case of total electrical or hydraulic failure. Also found on some commercial aircraft. Just enough power provided so you can find the ground softly instead of much harder because nothing is working.

https://en.wikipedia.org/wiki/Ram_air_turbine#Wing_mount

If you look at a picture of an older EA6B or the newer EA18 Growler the small propeller on the front of the large underwing pods are driving a generator to provide power to the pod. That is a RAT for that specific piece of gear.

bob

[Northwoods]

What is RAT?

BobR beat me to it.

Ram Air Turbine.  Basically a small fan that can drop into the airstream and provide electrical power in case of loss of engine power.  Some are big enough for limited hydraulic power too.

[BobR]

Chemical plants used to be the same way about a lot of stuff. I have people tell me they washed their hands in benzene and ear protection was a big wad of cotton near the door.

We used PD-680 as a degreaser, it worked like a champ. If we didn't have a 5 gal drum of that to pour over the gear we were working on we used freon as a degreaser. The only PPE we had was our dungarees. I remember my hands constantly being dry, cracked and bleeding. I thought that was a normal part of the job. 

bob