Dump fuel via fuel strainer in an emergency?

[nickmatic]

I was squirting precious fuel onto the pavement today like I do during every preflight, and it occurred to me that perhaps in an emergency, particularly a stuck gear forced landing, that perhaps one could dump the fuel from the tanks while circling before making the forced landing to reduce risk of fire on touchdown.

Would pulling the fuel strainer in flight be a safe way to accomplish this? I'd worry that the fuel would run back into the fuselage.

[MB65E]

Good idea, but it might get sucked back up in the belly panels...

Just depends on the airflow.

I bet you could burn it faster than it could drain it!

-Matt

[NotarPilot]

Being that it would likely get blown back up on the belly and soak your underside with avgas I could see more of a fire hazard being that the friction from a belly landing is likely to start a fire. Secondly, I think the fuel vapor in the tanks might be just as much of a fire hazard or more but I could be wrong.

[nickmatic]

Good point about the vapors. And I think I burn about 24 gph at WOT full rich so it could take up to 3.1 hrs to empty full tanks. Probably not a bad idea though...

[N201MKTurbo]

Has anybody ever caught no fire doing a wheel up landing? I always thought they were pretty low risk.

I found this article that talks about it and it confirms that fire after a gear up landing is extremely rare.

http://flighttraining.aopa.org/magazine/1999/February/199902_Gearup_Landings_Asphalt_or_Grass.html

Besides, the vast majority of gear up landings happen inadvertently. This article says that 95% are caused by just not putting the wheels down.

https://www.faasafety.gov/files/gslac/courses/content/83/779/FFP%20-%20Landing%20Gear%20Failure%20Course%20Text.pdf

To have to deal with this you would have to have two simultaneous system failures. The gear extension system would need to fail and the emergency extension system would need to fail. (Except for you Johnson bar people)

The best advice I got from these articles is to turn off the fuel selector and land as gently as possible on the pavement.

[Guest]

I was squirting precious fuel onto the pavement today like I do during every preflight, and it occurred to me that perhaps in an emergency, particularly a stuck gear forced landing, that perhaps one could dump the fuel from the tanks while circling before making the forced landing to reduce risk of fire on touchdown.

Would pulling the fuel strainer in flight be a safe way to accomplish this? I'd worry that the fuel would run back into the fuselage.

I once had a customer with a Piper Cherokee who accidentally left his strainer drain valve open. On takeoff the engine ran so poorly that he aborted the takeoff. It seems that air was being sucked into the fuel system.

Clarence

[John Pleisse]

First of all, here in the United Republic of Maryland, if you dump avgas on the pavement, you will be immediately engulfed by law enforcement and thrown in the environmental gulag. So give a hoot and don't pollute. Second, what is the flow rate of the gascollator? It's gotta be in the neighborhood of a Mooney fly-in prostate check. How much fuel could you dump? And if so, what is the purpose dumping avgas into your exhaust stream at altitude?

[Bob - S50]

Unless you fill the tanks for every flight (I don't), chances are that by the time you try to put the gear down and find it doesn't work, you probably only have 10 to 20 gallons left in the tanks anyway.  Depending on how much you trust your fuel gauges, I probably would not feel comfortable burning down to less than about 5 remaining.

 

Better to make a controlled gear up landing with 15 gallons on board than a gear up engine out landing because you ran out of fuel.

 

I'd use the extra fuel looking for the idea place to make that gear up landing.  Nice airport with maintenance available, maybe even a Mooney Service Center, nice level grass next to the runway with no buildings, ditches, roads, or taxiways running through it, etc.

 

Bob

[John Pleisse]

If you're gonna gear it up, do it where there is an FAA repair station or MSC. Amen to that. Great advice.

[mooniac15u]

 nice level grass next to the runway with no buildings, ditches, roads, or taxiways running through it, etc.

 

 

Landing in the grass sounds like a good idea but how confident can you be that there are no soft areas, low spots, etc in the grass?  Unless it is a turf runway it is an unknown.

 

Unfortunately, I have been in this exact situation.  I chose the asphalt.  During my debriefing with the FAA safety inspectors I mentioned having considered the grass and without hesitation they said, "you made the right choice."  I'm guessing they have seen the outcome of both choices.

 

Given the opportunity to set it down as gently as possible the damage was surprisingly not bad.  It was mostly limited to damaged belly panels, and of course the prop strike.

[nickmatic]

Good points here. I found an article that underscores the point about how relatively safe gear up landings are and also points out that asphalt is a better option than grass in most cases.

http://flighttraining.aopa.org/magazine/1999/February/199902_Gearup_Landings_Asphalt_or_Grass.html

[Vance Harral]

To have to deal with this you would have to have two simultaneous system failures. The gear extension system would need to fail and the emergency extension system would need to fail. (Except for you Johnson bar people)

 

In the electric gear airplanes, the emergency extension system just turns the same shaft the electric motor ordinarily turns.  If a failure to extend is caused by a problem with the shaft, rods, or gears internal to the actuator, that single failure kills both the normal and emergency extension mechanism.  This is the reason why the landing gear actutor ADs/SBs are so important to comply with.

[N201MKTurbo]

In the electric gear airplanes, the emergency extension system just turns the same shaft the electric motor ordinarily turns.  If a failure to extend is caused by a problem with the shaft, rods, or gears internal to the actuator, that single failure kills both the normal and emergency extension mechanism.  This is the reason why the landing gear actutor ADs/SBs are so important to comply with.

 

Of course, my point was that a gear up for mechanical reasons is a very rare event. The main cause is not putting the little plastic wheel in the down position.

 

But everybody thinks they are perfect and it couldn't happen to them, so they dwell on the things that are out of their control.

 

I've flown Mooneys for over 5000 hours without a mishap. Could I forget to put the gear down on my next flight? Of course I could. If you just look at the odds, I'm due.

[MB65E]

Hey, don't talk like that 201!!

-Matt

[M016576]

The biggest problem with "dumping" fuel via your gascolator is that you'll lose significant fuel pressure. If the motor doesn't outright quit, you lose a bunch of power. You can restart, but sustaining that state for long enough to dump a significant amount of fuel is unlikely.

That said, if you have a blockage in your gascolator, pulling the strainer could clear it and restore power. I've had that happen last winter when I had (suspected) ice crystals build up in my gascolator over a flight time of ~1.5hrs at ~ -10F ambient temp, resulting in a slow drop in fuel pressure, until I cleared it by momentarily pulling the gascolator, and restoring full pressure.

Edit: disclaimer- I do not condone any action that is not in accordance with the POH and sound piloting principles- my actions in past trouble shooting are provided here strictly for reference purposes- apply at your own risk!

[chrisk]

Being that it would likely get blown back up on the belly and soak your underside with avgas I could see more of a fire hazard being that the friction from a belly landing is likely to start a fire. Secondly, I think the fuel vapor in the tanks might be just as much of a fire hazard or more but I could be wrong.

This seems like a really good reason to not fool around with dumping fuel.   Especially if you could use that fuel to fly to a facility that is capable of repairing your plane.

[mooniac15u]

In case it helps with the decision about whether to spend time trying to dump fuel, FAR 23.967 specifies that fuel tanks must be designed to retain fuel during a gear-up landing or gear collapse.

 

(e) Fuel tanks must be designed, located, and installed so as to retain fuel:

(1) When subjected to the inertia loads resulting from the ultimate static load factors prescribed in § 23.561(b )(2) of this part; and

(2) Under conditions likely to occur when the airplane lands on a paved runway at a normal landing speed under each of the following conditions:

(i) The airplane in a normal landing attitude and its landing gear retracted.

(ii) The most critical landing gear leg collapsed and the other landing gear legs extended.

In showing compliance with paragraph (e)(2) of this section, the tearing away of an engine mount must be considered unless all the engines are installed above the wing or on the tail or fuselage of the airplane.

[Hank]

In case it helps with the decision about whether to spend time trying to dump fuel, FAR 23.967 specifies that fuel tanks must be designed to retain fuel during a gear-up landing or gear collapse.

.

That's nice, and I've never heard of a simple gear up causing a fire without additional complications, but our Mooneys are CAR 3 planes not FAR 23. If I knew I had gear problems, there's a lot of things I'd worry about before the idea of dumping fuel ever occurred to me.

[mooniac15u]

That's nice, and I've never heard of a simple gear up causing a fire without additional complications, but our Mooneys are CAR 3 planes not FAR 23. If I knew I had gear problems, there's a lot of things I'd worry about before the idea of dumping fuel ever occurred to me.

 

Some Mooneys were only certified to CAR 3 standards, many are compliant with 23.967 per the TCDS.  The OP's plane is an M20K which was certified in compliance with 23.967.

 

Even with original CAR 3 certification do you believe that the fuel tank design was fundamentally modified for the M20K vs your M20C to meet the new standard?

[Hank]

I thought all Mooneys have the same TCDS. Given that, how can the certification standards be different?

[mooniac15u]

I thought all Mooneys have the same TCDS. Given that, how can the certification standards be different?

It is one TCDS but the various models are all listed separately with each having a "certification basis" section which outlines which regulations applied to the certification. It can be found here: http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgMakeModel.nsf/0/e74974516b2c5ee886257c3500689e02/$FILE/2A3_Rev_53.pdf

[drbob]

Gear problem:

    Long final, stop engine, level the prop, trim, retract flaps when abt 5-10' off,

  progressive FULL aft yoke as it settles,

 considerable ground effect so, long float & touchs at abt 35- 40 mph +, smooth grass is best, prop, flaps untouched.

Then the real fun begins, now how to get this birthday up cake off the ground!

          

       disclamer don't try this at home, for professionas only 

                                                                                            your results may vary! 

                                                                                    Just one technique.

                                                                                                                            drbob        

[Hank]

My first choice would be smooth concrete, followed by asphalt. With grass, it's never completely smooth, and may be soft and wet. All you need is a low spot or a soft spot, and something will dig in and spin you sideways, pull something off (gear door? belly strobe?) or in extreme cases, flip you.

With my 3-blade, there's no saving it, so the landing will be normal and as slow as possible, on the smoothest, hardest service around. Happened to my plane before me, unplanned. They slide along and stop, no spinning, jumping or bumping. Some are repaired, some are totaled. YMMV. Here's to not having this emergency!

[jetdriven]

Gear problem:

    Long final, stop engine, level the prop, trim, retract flaps when abt 5-10' off,

  progressive FULL aft yoke as it settles,

 considerable ground effect so, long float & touchs at abt 35- 40 mph +, smooth grass is best, prop, flaps untouched.

Then the real fun begins, now how to get this birthday up cake off the ground!

          

       disclamer don't try this at home, for professionas only 

                                                                                            your results may vary! 

                                                                                    Just one technique.

                                                                                                                            drbob

I think this is the new record for most amount of bad advice ever published in one post. Don't take my word for it, just compare to anything published by the FAA, AOPA, BPP, etc.

[drbob]

See the disclamer,

        touches  so far aft only belly and flap supports scraped, worked for me.