Vettster

Just wondering what its real purpose is? When the engine is not running, the fuel pump is not active. Also we shut off the valve. If the plane goes into fail-safe the pump stops working. When the engine is running.. all it does is stay in the open position.

Many of the Propane users(my self included) dont use the Gas Solenoid anymore.

Do we really need the Fuel Solenoid?

gunradd

My Feedback: (9)

The main reason is for starting. You still have 2 fuel solenoids. One is for the beginning of the start and the main fuel valve opens at switch over. Also it helps keep the prime to the pump when you shut it down.

Vettster

Ok.. I kinda see what your getting at. But the pump would not activate till it was told to add the kero, and at that same time is when the solenoid would open.

As far as keeping the prime.. The pump will not let fuel thew unless powered up. Again acting like the solenoid.

Thoughts to ponder?

Vettster

It seems to me to be a redundant gateway for the fuel. As soon at the pump is on the gate is open. When its off its closed. Not really a big deal until the solenoid fails. Why not eliminate that all together..

GSR

My Feedback: (145)

I always thought it was in case the pump circuit failed and the pump went into runaway-then the shut off signal closed the solenoid-S

hmjets

Most important function is to avoid the engine being flooded by fuel,when the fuel tank is filled.

ira d

good point, Although I have heard of ECU causing the pump to runway and the solenoid did not stop the fuel. But I always thought it was the AMA that came up with the
solenoid requirement. Also I think in some installs they can prevent turbine flooding if you forget to close the manual valve during refueling.

Gonzalo38

A fuel solenoid should help you to avoid flooding the turbine in case you forget to close your fuel valve. Seen a couple of planes burning because the owner forgot to close it....

I prefer to have one on board for safety reasons.

gunradd

My Feedback: (9)

If the pump didn't turn on until switch over you would never get ignition....

Your ignition fuel goes through a different valve to get the fire started and go into preheat. It's not until switch over(half way through the start) does the main fuel valve open to finish the start and run.

invertmast

My Feedback: (23)

He doesnt have a kero start turbine according to his original post

gsmarino2000

My Feedback: (2)

Vettster,

I doubt the pump is tightly sealed against leakage into the turbine when you are filling the tank, so as Gonzolo said, this could prevent accidentally flooding the turbine. Also the ECU/FADEC driver switches (MOSFETs, I presume) are a potential failure mode. It would be possible for them to short closed so that the pump received full voltage. The ECU could not shut it off. In such a scenario, the solenoid acts as a redundant back up to let you save your plane.

Greg

causeitflies

I was running an engine on the stand the other day. The tank, air trap and lines were empty and I wasn't using a shutoff valve. As I filled the tank the fuel filled the lines and made it's way past the pump and most of the way toward the engine leaving just a few inches needed to prime. I had the fuel line disconnected from the engine anyway but if this was in a plane with no valve and full lines the next start would be exciting.

basimpsn

My Feedback: (5)

It's a sure fire if you don't have a fuel solenoid to stop the fuel from flowing into the engine during fueling...But the engine can work without it if you remember to manually use the festo shutoff valve.

Vettster

Some Really great reply's here guys!!!

Yes I was thinking Gas start, but I wasn't really clear on that. sorry.

In any case my OP cleared up many un answered questions, like does the fuel pump allow fuel thew when not powered up. For sure I now see that the solenoid is going to stay in my plane...but it just got me thinking.. what if?


Thanks guys..

gunradd

My Feedback: (9)

Even with kero start you have one valve for ignition and preheat and another for running. The fuel for starting comes out near the ignitor for ignition and preheat.

rhklenke

My Feedback: (24)

From AMA document 5010-a, "SAFETY REGULATIONS FOR MODEL AIRCRAFT POWERED BY GAS TURBINES":

The fuel system shall have two fuel shut off provisions, one of which is manual and the other one must be remotely operated. An ECU operated shut down is compliant as a remote shut off if it closes with loss of power.

Thus, for most of us in the US with standard off-the-shelf engines, the ECU-controlled fuel solenoid is required.

Bob

flyinfool1

My Feedback: (2)

The AMA rule does not use the word valve. It just says you must have 2 ways to shut of fuel flow.
The fuel pump does meet the requirements of the AMA rule. It is remotely operated, it is operated by the ECU, Loss of power will shut down flow since we are using positive displacement pumps. I still have, and will continue to have a fuel solenoid in all of my jets. But as the rule is written, if you do not need the solenoid valve for startup, I don't know that it is required per the rule.

basimpsn

My Feedback: (5)

If I remember correctly the older manual start ram engine didn't use fuel or gas solenoid.

rhklenke

My Feedback: (24)

I did not think of it that way. When I read it, the phrase "closes with loss of power" implies a normally closed solenoid valve - a fuel pump does not "close" in the normal sense one thinks of "opening" and "closing".

You are right though in that the wording is ambiguous. I don't know what the intent was when the rule was originally written, but my guess is that, since most production turbine engines have (or have had, RAMs not withstanding), a fuel solenoid, that it was intended to require them, along with a manual valve.

For my part, I have never had a failure of a fuel solenoid, but in spite of myself, I quite often forget to check the manual shutoff before fueling, and I don't think that just a stopped fuel pump is enough to keep from flooding the engine during fueling - what with the high speed fueling pumps most of us use...

Bob

Gonzalo38

Bob:

A fuel solenoid should always be closed when not energised, but I've seen a couple of the failed and airplanes getting hot starts because of that. A lot of people forget to close the fuel shutoff valve (It has happened many times to me....) and in that case, the only protection you have against flooding is the solenoid. Problem is when the solenoid gets stuck or something is not allowing it to completely close. As you said, the fuel stations that we are using to refuel our jets are powerful enough to move the fuel pump. Fuel will start moving to the turbine and you will have a massive hot start.

I agree that solenoids can be another point of failure, but it is another safety element that I would never take it out of my planes. The upsides are bigger than the downsides.... specially when you are talking about some of the bigger and more expensive jets.

RSO

I have had one solenoid failure on the start side, resulting in a closed solenoid, therefore no fuel flow. One solder joint on one wire had failed. Resoldered wire and all was well. This would seem to indicate that a solenoid fails in a closed position.

Jerry

Gonzalo38

Jerry:

I've seen that a couple of times. Fortunately for us down here, our local turbine distributors carry a good amount of little spare parts like solenoids so we've never been out of flight because of them.

One thing we always do at our club, is to open all the hatches before we start our turbines. In that way we can see fuel flowing or not flowing into the lines and that makes diagnostics in case of failure easier. Also it helps to see if something is wrong (ex: flames) and allow us to react faster. I've seen that in many places they start the airplanes without opening the hatch, without connecting the turbine terminal and making some tests to see if the turbine is performing 100%. That for me is a recipe for failure..... maybe not today, but at some moment.

RSO

You're absolutely correct. Actually was able to do a field repair in this case.

Jerry

flyinfool1

My Feedback: (2)

You are correct that a fuel solenoid will always fail in the closed position, IF it is an electrical failure. A mechanical failure can be either open or closed. A mechanical failure could be many things, a broken spring that no longer closes the valve, a piece of dirt/debris holding the valve open, the valve seat wearing out or many other things that would be very unlikely.

Gary Szetlak

My Feedback: (13)

I have had solenoids leak fuel past and fill up the engine (more than once unfortunatly) and have had hot flaming starts, a hard leason to learn but now I will always have an additional manual shutoff valve between the solenoid and engine