On Jan 14, 6:37 pm, Bertie the Bunyip wrote:
akiley wrote :

On Jan 14, 4:52 pm, Bertie the Bunyip wrote:
akiley wrote
innews:5c24ef75-4385-4897-a75d-





om:

On Jan 14, 3:33 pm, Bertie the Bunyip wrote:
akiley wrote in
news:2e7dbffb-645c-49b6-9687-
:

Hi All, I'm working on my multi rating in a Beech Duchess. I'm
curious about an item that doesn't seem well covered in the POH
and elsewhere for that matter.

What if you loose one engine at altitude, allowing plenty of
time to try to fix. You determine that you ran the right tank
dry of fuel. According to the fuel diagram, you should be able
to run both engines off one tank. The fuel line exits each tank
and splits: one going to the opposite fuel selector and one
going to the closest engines fuel selector.

If this is doable, why is it not talked about more? It's not a
"fix" option on the checklist and not discussed in the text of
the POH. Crossfeed is considered an emergency operation
according to the POH, and also "level flight only". Could this
be why? Possible fuel starvation on the crossfeeding engine from
maneuvering to land, where it may be safer to feather and secure
the dead engine and do your one shot landing.

... akiley

I have no idea what you're asking here. If you've lost an engine,
why would you be needing to run both off one tank?

Now, if you mean that you still have a long way to go and that
you'll run one dry before you get where you are going, then , yes,
that's what it's for.
You also want to alternate a bit to keep any imbalance from
getting crazy. I haven't flown a duchss n a long time, but I don't
remember there being anything too strange about the crossfeed
arrangements. But if you lost one there's nothing stopping you
from crossfeeding from the oppostie tank. Likelywise, if you have
a leak in one tank, there's no reason I can see you can't run both
engines off of the remaining tank. Sounds like they are (quite
rightfully) discouraging 2recreational crossfeeding" that some
guys do just to "balance em out perfectly" This usually leads to a
massive imbalance, or even worse, having both engines flame out
due to ou getting distracted and forgetting.

It happens.

Bertie

In essence, I was asking if there was any reason not to run both
engines off one tank. In singles, "switch tanks" always seems to
be part of the emergency checklist for a rough engine, yet in the
Duchess POH (and a Seneca I for that matter) "crossfeed" isn't
mentioned as a diagnostic step where it seems like is should be. I
was wondering if I had missed something.

OK, if I'm following you, you're suggesting that you've lost an
engine for no apparent reason. You decide that it might be a fuel
problem, so you want to feed off the tank on the opposite side to see
if that fixes it.
Sounds like a good idea to me. You would have to be very, very
careful that it wasn't a fuel line on the failed side that caused the
problem in the first place, otherwise you could lose all the fuel.
That's what happened to that A330 that deadsticked into the Azores.
But it sounds like a reasonable thng to do if that is what you
suspect the problem is. Just make sure you do it slowly and
deliberately. you don't want to end up gliding due to a poor
selection. You might also consider, on the day, the wisdom of
relighting an engine with a fuel problem. It's all a trade off of
various risks. Wx, how far you have to go vs how much gas you got
left, that sort of stuff. If you don't really need it to get where
you are going, it might be better not to take the risk. If you are in
the middle of a mountain range and you need it to keep your altitude
above MORA at night, different story. Not that you should be there
anyway. Manufacturers, the FAA and schools will steer you towards the
checklists and procedures for some very good reasons. Experience with
some of these situations has produced a pattern of th emost likely
causes and the results of getting too creative with the systems. If
they recommend you do something a certain way, do it that way. But,
if you 're off the page, knowing how the system works will enable you
to analyse the problem with a good chance of a solution.

Bertie

Thanks for the good point. Remember in the original post I made a
scenario where I exhausted the fuel in the right tank. Fuel pressure
and quantity gauges confirmed this. So I decide to try to crossfeed
from the good engine side to the engine that I lost due to fuel
starvation. But good point. What if I lost all the fuel in that tank
because of some problems like a leak that may effect the full tank if
I crossfeed.

If you exhausted the fuel in one tank with a simple system like a
Duchess or Seneca has, it can only be because there wasn't much to begin
with ( you wouldn't do that, right) or because it's spilling out
somewhere it shouldn't. If you can see it coming out of the tank ( left
the cap off? ) then you might have a case for x-feeding. If not, it
might be leaking downstream of where the other tank joins into the
failed side's fuel system.
One other reason you might not be getting fuel is a failed fuel pump.
Maybe both the elec and mech pump is gone on one side. The elec pump on
th eoposite side should be able to pressurise the fuel system on the
opposite side. It did in at least one airplane I have flown. Very
unlikely, I know, but it could be and this one has happened to me once
in a twin Beech on the ground.

I seem to recall some twins had problems with fuel lines chafing,
which cased the fuel line to rupture draining the tank into the wing
area behind the engine somewhere. Maybe you wouldn't want to try to
restart that failed engine using crossfeed! Also, can't a clogged
fuel tank vent cause a vacuum, then fuel starvation?

So maybe the aircraft manufacturer doesn't want to suggest the option
of restarting a failed engine by crossfeeding from the opposite engine
because: It might be dangerous in some cases like you mention. Fuel
leaking internally. Maybe securing that failed engine, which turns
off fuel and electricity on that side is a safer option.

.... akiley