Fuel leakage during in-flight refueling

When refueling using the probe and drogue system, is it commonplace to have
fuel leakage from the drogue? At my day job, we have a foreign customer
asking about the resistance of an engine to fuel ingestion during refueling.
Apparently it is something of a problem for them, but they have not been
able to give us any specifics.

I thought someone here may have some real world experience they could share.
Do you get a brief mist of fuel when you disconnect? ... or can you
experience an continual "dribble" down the probe during the transfer? Any
info or war stories would be helpful.

Regards,

Mark Johnston

As far as I saw this on a sort of film that is a mist, indeed. Bear in
mind the fact that in many planes the refueling probe is often quite
distant from the jet intake.

Any dumped fuel seemingly turns into mist as well.

One story I've heard from civil aviation: it happened probably in
France in the 1980s, when a passenger jet exploded after unluckily
coming into the cloud of fuel it dumped one lap before.

In Britain in WWII there was a weird idea to spray fuel in the air, to
make V-1 missile engines suck it, fly longer than expected, and then
overfly their targets.

Best regards,

Jacek

mark johnston wrote:
When refueling using the probe and drogue system, is it commonplace to have
fuel leakage from the drogue? At my day job, we have a foreign customer
asking about the resistance of an engine to fuel ingestion during refueling.
Apparently it is something of a problem for them, but they have not been
able to give us any specifics.

I thought someone here may have some real world experience they could share.
Do you get a brief mist of fuel when you disconnect? ... or can you
experience an continual "dribble" down the probe during the transfer? Any
info or war stories would be helpful.

Regards,

Mark Johnston




May get a wee bit when you pull out but no leakage when refueling.

I am stretching here, but I seem to recall this is the reason that the
AAR probe on the A-4 Skyhawk was revised from a straight design to one
that incorporated a "dog leg." If I recall correctly, when the
Scooter backed away from the basket, a valve in the end of the probe
would sometimes allow a puff of fuel to escape. In the original
straight design, the puff would then be promptly ingested down the
starboard engine intake. This occasionally would do bad things to the
engine and create a bad day for the pilot. The "dog leg" design
moved the path of the fuel puff far enough away from the inlet to
prevent ingestion.

If I am wrong, I hope someone will correct me on this.

Blue skies . . .

On 24 Mar 2005 09:36:13 -0800, "John" wrote:

I am stretching here, but I seem to recall this is the reason that the
AAR probe on the A-4 Skyhawk was revised from a straight design to one
that incorporated a "dog leg." If I recall correctly, when the
Scooter backed away from the basket, a valve in the end of the probe
would sometimes allow a puff of fuel to escape. In the original
straight design, the puff would then be promptly ingested down the
starboard engine intake. This occasionally would do bad things to the
engine and create a bad day for the pilot. The "dog leg" design
moved the path of the fuel puff far enough away from the inlet to
prevent ingestion.

If I am wrong, I hope someone will correct me on this.

Blue skies . . .

Never tried to put my broad butt in a Scooter, but other aircraft with
the dog leg in the probe, such as the F-100, did it to move the
refueling point into quieter air out of boundary layer or to improve
pilot visibility for hook up.

The very small amount of fuel that sprayed at disconnect either from a
drogue or off the boom from a receptacle surely wouldn't do much to an
engine under normal conditions. In the F-105, the spray of mist would
fog the windscreen and then blow off in two seconds. Any fuel that
went down the intake could be sniffed in a second or two as it came
through the pressurization system--which is why the checklist for
refueling specified 100% oxygen.

Ed Rasimus
Fighter Pilot (USAF-Ret)
"When Thunder Rolled"
www.thunderchief.org
www.thundertales.blogspot.com

I knew I was on thinning ice, but at least I know that being shot down
by Ed means I have been shot down by one of the better ones.

I just found this at http://www.skyhawk.org/2C/productionhistory.htm
regarding design changes to the A-4F.

"A unique recognition feature that first appeared on the A-4F was the
"bent" aerial fueling probe. The probe was so configured to preclude
electronic inteference with the wide-angle target acquisition
system."

Also found this at http://www.airtoaircombat.com/detail.asp?id=57 :

"The A-4M was fitted with a revised refuelling probe which canted out
to starboard to precent interference with a wider-angle target
acquisition system."

Now that Ed has thrown the thrid strike, it is time for me to head back
to the dug-out and resume lurking. (Smiling)

blue skies . . .

P.S. to Mr Rasimus - Is the new book actually out yet (fingers
crossed)?

On 24 Mar 2005 10:18:18 -0800, "John"
wrote:

I knew I was on thinning ice, but at least I know that being shot down
by Ed means I have been shot down by one of the better ones.

I just found this at http://www.skyhawk.org/2C/productionhistory.htm
regarding design changes to the A-4F.

"A unique recognition feature that first appeared on the A-4F was the
"bent" aerial fueling probe. The probe was so configured to preclude
electronic inteference with the wide-angle target acquisition
system."

Also found this at http://www.airtoaircombat.com/detail.asp?id=57 :

"The A-4M was fitted with a revised refuelling probe which canted out
to starboard to precent interference with a wider-angle target
acquisition system."

Now that Ed has thrown the thrid strike, it is time for me to head back
to the dug-out and resume lurking. (Smiling)

blue skies . . .

P.S. to Mr Rasimus - Is the new book actually out yet (fingers
crossed)?


Don't be too hasty, John.

It is true that the off-set probe was installed as part of
AFC 461, titled Avionics; AN/APS 117 Shrike Target
Identification Acquisition System and it's also true that it
was installed because the straight probe interfered with the
sensor operation.

However, it was also found to prevent fuel vapor
ingestion/explosion when the coupling leaked during
in-flight refueling. A second part to the AFC (Part 2) was
issued a couple of years later to authorize off-set probe
installation on all aircraft not covered under the original
AFC. The part 2 title was changed to Fuselage; Offset IFR
Probe Installation and TIAS, Provisions For. That's why
some TA-4s had the off set probe. The original AFC was for
"designated" A-4Es and Fs.

I remember reading through A-4 accident summaries a few
years ago and it seemed that the USN/USMC lost and average
of a plane a year to fuel vapor ingestion during IFR.

In May 83 NAVAIRSYSCOM message 260109Z, all A-4 aircraft not
equipped with the off-set probe (AFC-461) were restricted
from aerial refueling from KC-135 aircraft equipped with the
boom to drogue adapter with the exception of operational
necessity.

The restriction was in response the loss of a TA-4J due to
the leaking/ingestion problem and several more reports that
it occurred. I don't remember that restriction ever being
lifted.

Tom Debski

On 24 Mar 2005 10:18:18 -0800, "John" wrote:

Now that Ed has thrown the thrid strike, it is time for me to head back
to the dug-out and resume lurking. (Smiling)

blue skies . . .

P.S. to Mr Rasimus - Is the new book actually out yet (fingers
crossed)?

Actually, we don't throw strikes or even brush-backs in the better
newsgroups. We just share knowledge and hopefully get a bit wiser.

As for the book, coincidentally just this week I got a contract offer
from St. Martin's Press and the book which was delayed by the failure
of Smithsonian Books is now back on track.

The book should revert to the original title I had for it which is
"Palace Cobra: Fascination With A War" rather than the previously
announced "Phantom Flights, Bangkok Nights" (Smithsonian imposed, but
it sounded to me like a grade B porno movie.)

Anticipated availability won't be until the end of the year with the
new publisher.

Ed Rasimus
Fighter Pilot (USAF-Ret)
"When Thunder Rolled"
www.thunderchief.org
www.thundertales.blogspot.com

"John" wrote...
I am stretching here, but I seem to recall this is the reason that the
AAR probe on the A-4 Skyhawk was revised from a straight design to one
that incorporated a "dog leg." If I recall correctly, when the
.. . .

If I am wrong, I hope someone will correct me on this.

All too true! In the later years of the Scooter, inflight refueling was
prohibited with the straight probe.

I think the probe was "bent" to get the receiver out of the tanker's
wash. Most navy planes with probes had the probe out in front of the
pilot to make it easier to plug in. Some like the Fury had the probe
way out and were a bitch to plug. Crusaders probe was behind the pilot
and made for a few missed plugs. Little fuel leakage, even into the
intake, was no problem. But some guys just weren't happy unless they
could bitch about something. I liked to get the gas no matter some
leaks. Beat punching out all to heck.