Using 100LL instead of Jet A in a pinch?

Is it a big deal using 100LL instead of Jet A in a Beechcraft 1900?

A charter I was flying with landed at an airport to refuel only to find empty fuel tanks and noone to deliver fuel to the airport. After an hour or so, the pilots dipped into the 100LL tank at the airport and we continued on our way to another airport with Jet A.

One of the guys called his dad, an A&P mechanic, who never heard of such a thing.

It is permitted on many aircraft. Not a big deal, except that the engine has to be inspected after you get to around 10 or 100 hours of cumulative operating time.

A 1900 is essentially a big Kingair, P&W engines, so its probably approved, but I don't know for sure.

You could probably google up the appropriate part of the 1900 POH if you are really curious.

I wouldn't feel to good about operating with a mix of JETA and 100LL, so I'm glad I've never had to do it.

We have had based turbine aircraft (cheyenne) periodically blend avgas in there fuel tanks. This was to halt microbial growth in the fuel system. It was not 100% avgas. I would refer to the POH.

Permissible but as stated, only for a limited time and a hot end inspection is usually required.

For the US Navy and the C-12 with the PT6A engines if you use leaded fuel you have to do a computation using the amount of leaded fuel and the amount of fuel on board and then monitor how many hours each engine was run when the leaded fuel was pumped into the tanks.
I think that you use one complete refueling (all at once or multiple fuelings) and then the tanks are considered purged.
The reason was that when burned the leaded fuel left deposits on the (I think) power turbine blades which can cause hot spots and is also a concern for the mechanics working on the hot section.
I also think that the number of hours you could operate the PT6A on leaded fuel 150 hours during any overhaul period leaded fuel.

The engine was authorized to burn JetA, JetA1, JetB, JP4, JP5 and JP6 as regular fuel.
Authorized alternatives were all grades of AVGAS and diesel fuel.

Of course I could be wrong.

The king air 200 I used to fly was limited to 10 hours on 100LL. If I remember right there was a degradation in performance that went along with it.

Ran 400 gallons of avgas in a lear 25 once...bet that line guy reads the truck label more closely next time. It is allowed in the king air 350, limited to ten hours as previously mentioned, some aircraft have an additional charge towards overhaul times too

Got off my lazy butt and pulled my 350 POH, 150 hours of avgas between overhauls, both standby pumps must be operative, crossfeed must be operative for flights above FL200. It has the Pratt PT6A-60A

As stated above 100LL can work in a pinch. My 135 operation will not allow 100LL in turbines at all. In Alaska it's probably just another day to push the limits of what is allowed...

Edit...if it's the other way around...Jet-A in a piston...DO NOT GET ON BOARD...!!!!

100LL has a tendency to deposit lead on the turbine blades and stators, resulting in degradation of performance over time. Also, the fuel controls on turbine engines are calibrated to run optimally with Jet A; the specific gravity of AVGAS is different, and will result in further inefficiencies and just general weirdness, due to improper fuel trims.

In an emergency, hell yes, pump away: A turbine engine will burn just about anything flammable.

In reality, check the POH and Maintenance Manuals for limits and subsequently required inspections/engine washes.

In some engines your next hot section inspection will be pretty expensive due to parts that need to be changed. TFE331 iirc. Not sure about the long term MX costs when it comes to 1900s...

This is also correct for the King Air B200.

Our old boss used to fly all kinds of stuff in the USAF.

Back when they would refuel off of the old KC-97 they would get some
avgas from the KC-97's own supply if the JP fuel was getting low.
He said there was no performance change he could see.
Only different color of exhaust soot in tail pipe.

...and for the C90 I used to fly. We had to use 100LL once leaving Mexico and the owner was about to have kittens worrying about the overhaul cost. Accumulated 12 hours total if memory serves.

ONLY in a pinch. Read your POH and the engine MM for the penalties of use. 100LL has LEAD in it and the lead is a huge NO NO on hot turbine blades. Been a jet engine mechanic for over 25 years now. Pratt PT-6, JT-15D, PW305 and 308's, All Garrett/Honeywell TFE731 series 2-3-4-5-20-40-50-60, AS907, and CFE738. Like the other posts said, Go are going to be doing a hot section/MPI very soon after use. And thats going to cost you $$$$$.

+1 on this

One other thing that nobody has mentioned is that the possibility of a hot start goes up as does the tendency to overtemp an engine when using AVGAS. Throttle lever angle and throttle response is changed from what the pilots are use to due to changes in specific gravity and volatility from Jet A.

As a side note; Beechcraft will not allow the use of K-1 kerosene but Pratt and Whintney will. And as we all know the Airframe manufacterer wins......

Thanks, guys. At least it is permitted to some extent. I have some late night reading to do. At least the pilots were really reluctant to do this.

IIRC, in the lear series the pilot could go in and manually reset the Fuel Control Computer based on what was being burned. The POH had the charts to do this. I just got rid of my B1900 POH so that is one I cannot look up.

ka

The 20 series lear could run it, just like ou say, set the fuel computers for avgas. Problem was that there was an altitude limitation, low twenties best I remember, if you saw the fuel burn on a twenty series lear your jaw would drop....much less at low altitude...300+ gallons the first hour

I know that the King Air 200 was approved for it with the aforementioned time limitations. I flew and old Citation 501 that was approved with a time limitation, as well. I am flying a Citation 510 Mustang now and it is not approved.

Brian

Strictly from memory, but I believe the 1900's limitation was FL240 on 100LL, and I believe less than 100 hours, and the fuel pumps couldn't be MEL'd and had to be on above 180.

And, IIRC, the big issue was lead fouling on the compressor blades for 100LL, and water formation for non aviation gas.

Had several pilots do it. (Landed at an airport on the other side of town which didn't have Jet A. They'd put in 50-100 gallons of 100LL and hop over to get a fuel load then hop back.)

Lear 20 series don't have fuel computers, but I think they do have an SG selector on the FCU, it's been a long while since I worked on a 25 so I could be wrong. 30 series have EECs or DEECs which do have a rotary switch for SG selection. I have seen a Turbo Thrush/ PT-6 that was placarded by the fuel filler that it was approved for Jet-A, Jet-B, K-1, Diesel, and 100LL. The "lead" in 100LL is tetra ethyl lead, not to be confused with Mb.

The lear 20 series has a mechanical "computer" to compensate for fuel density, it has adjustment settings for pretty much all types of fuel. Problem is that they are waaay back in the tail through the hell hole, when you are 6'3" 250lbs it is a very tight squeeze

Unable to comply with required maintenance procedures. Oval peg is too large for round hole.

I had to call my boss one night and tell him that a certain pneumatic valve in the pylon on a DC-10 wasn't getting changed that night, for that very reason.

Yeah, I'm 6ft 175 lbs and our other mechanic was 5'6 200lbs so I am very familiar with the Lear hellhole, lol. I have changed a few DEECs which are way back there on the 35's, and of course we didn't have patch cables to adjust them before installation, so it was like, install it, run it, pull it out and adjust it, install it, run it, repeat until it's right. That sucked. I'm not an engine overhaul guy, but I don't think the 100LL will do any damage as whatever deposits are left on the hot section will be burned off as long as the limitations in the poh are observed. Due to mfr liability concerns they would not allow it if there was any chance it might cost them money.

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