Twin take off on one engine?

On Thu, 3 Sep 2009 17:42:52 -0700 (PDT), Richard wrote in
:

... I googled the heck out of it and could not find any thing single
engine take off of a 747.

I couldn't find anything I thought was reliable--some
claims and counterclaims on groups or forums like this.

What is clear is that the 747 can and has done lots of
ferry flights with one of the four engines inoperative.

If you're already up in the air with decent altitude
and a light payload, one engine might keep you in
the air.

My personal bet is that one engine won't do for liftoff.
Two would probably be OK. Three--people have done it,
so there's no doubt about it.

Marty
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You could probably do it in a skymaster. We had a 58 barron loose one
engine and was almost impossible to taxi. No was you could take off. Legal
or not

On Sep 4, 8:47*am, Clark wrote:
"Flaps_50!" wrote in news:d7b4faf4-4167-46cd-8692-
:



According to the data I can find, the 747 can't climb on one engine so
how can it take off?
Cheers

Hmmm, empty weight is about 360,000 lbs plus a little fuel and 50,000 lbs of
thrust. It aught to work. I suspect your data are in error or perhaps you're
considering a loaded 747.


It comes from the certification requirements of a commercial 747
climbing on 3 engines. The excess thrust is calculated from the rate
of climb in that condition and knowing that 1 HP is 33,000 ft lbs /
rminute. Perhaps my math is wrong but I don't calculate an excess
thrust of 120,000 lbs... What do you get?

Cheers

On Sep 4, 3:26*pm, "Martin X. Moleski, SJ"
wrote:
On Thu, 3 Sep 2009 17:42:52 -0700 (PDT), Richard wrote in
:

... I googled the heck out of it and could not find any thing single
engine take off of a 747.

I couldn't find anything I thought was reliable--some
claims and counterclaims on groups or forums like this.

What is clear is that the 747 can and has done lots of
ferry flights with one of the four engines inoperative.

If you're already up in the air with decent altitude
and a light payload, one engine might keep you in
the air.


Wasn't there was a case of a single engine landing with no go around
being possible?
Cheers

"Clark" wrote in message
...
"Flaps_50!" wrote in news:2ce85d20-5c84-4425-a1bf-
:

On Sep 4, 8:47 am, Clark wrote:
"Flaps_50!" wrote in news:d7b4faf4-4167-46cd-8692-
:



According to the data I can find, the 747 can't climb on one engine so
how can it take off?
Cheers

Hmmm, empty weight is about 360,000 lbs plus a little fuel and 50,000
lbs
of
thrust. It aught to work. I suspect your data are in error or perhaps
you
're
considering a loaded 747.


It comes from the certification requirements of a commercial 747
climbing on 3 engines. The excess thrust is calculated from the rate
of climb in that condition and knowing that 1 HP is 33,000 ft lbs /
rminute. Perhaps my math is wrong but I don't calculate an excess
thrust of 120,000 lbs... What do you get?

Cheers

What I get is that I suspect your numbers are at gross weight. I suggest
looking at the problem as stated rather than making up your own
conditions.


--
---
there should be a "sig" here

What I get is the latest successfull troll: please ignore him.

On Sep 11, 1:02*am, "Peter Dohm" wrote:
"Clark" wrote in message

...



"Flaps_50!" wrote in news:2ce85d20-5c84-4425-a1bf-
:

On Sep 4, 8:47 am, Clark wrote:
"Flaps_50!" wrote in news:d7b4faf4-4167-46cd-8692-
:

According to the data I can find, the 747 can't climb on one engine so
how can it take off?
Cheers

Hmmm, empty weight is about 360,000 lbs plus a little fuel and 50,000
lbs
*of
thrust. It aught to work. I suspect your data are in error or perhaps
you
're
considering a loaded 747.

It comes from the certification requirements of a commercial 747
climbing on 3 engines. The excess thrust is calculated from the rate
of climb in that condition and knowing that 1 HP is 33,000 ft lbs /
rminute. Perhaps my math is wrong but I don't calculate an excess
thrust of 120,000 lbs... What do you get?

Cheers

What I get is that I suspect your numbers are at gross weight. I suggest
looking at the problem as stated rather than making up your own
conditions.

--
---
there should be a "sig" here

What I get is the latest successfull troll: *please ignore him.

I see, discussion using physics and aeronautics about real aircraft
performance is a troll to you. You clearly prefer BS.
The 747 figures I used: empty weight 403,000 #, MTOW 870,000 #.
Minimum fuel 70,000 #, thrust available 60,000 #. That gave me TOW of
473,000 # which is quite a bit more than Clark 'estimated' so the drag
would be proportionally higher. In the absence of any ref to the
claimed actual takeoff on one engine, it sounds like urban piloting
myth.

On Sep 11, 2:19*pm, Clark wrote:
"Flaps_50!" wrote :



On Sep 11, 1:02*am, "Peter Dohm" wrote:
"Clark" wrote in message

.. .

"Flaps_50!" wrote in
news:2ce85d20-5c84-4425-a1bf
-
:

On Sep 4, 8:47 am, Clark wrote:
"Flaps_50!" wrote in
news:d7b4faf4-4167-46cd-86
92-
:

According to the data I can find, the 747 can't climb on one
engine
*so
how can it take off?
Cheers

Hmmm, empty weight is about 360,000 lbs plus a little fuel and
50,000 lbs
*of
thrust. It aught to work. I suspect your data are in error or
perhaps you
're
considering a loaded 747.

It comes from the certification requirements of a commercial 747
climbing on 3 engines. The excess thrust is calculated from the rate
of climb in that condition and knowing that 1 HP is 33,000 ft lbs /
rminute. Perhaps my math is wrong but I don't calculate an excess
thrust of 120,000 lbs... What do you get?

Cheers

What I get is that I suspect your numbers are at gross weight. I
sugges
t
looking at the problem as stated rather than making up your own
conditions.

--
---
there should be a "sig" here

What I get is the latest successfull troll: *please ignore him.

I see, discussion using physics and aeronautics about real aircraft
performance is a troll to you. You clearly prefer BS.
The 747 figures I used: empty weight 403,000 #, MTOW 870,000 #.
Minimum fuel 70,000 #, thrust available 60,000 #. That gave me TOW of
473,000 # which is quite a bit more than Clark 'estimated' so the drag
would be proportionally higher. In the absence of any ref to the
claimed actual takeoff on one engine, it sounds like urban piloting
myth.

While your efforts are some-what commendable (at least you tried) they
don't fit the timeframe and conditions. It was a one time deal on an early
model 747. Lower empty weight and minimum fuel wouldn't necessarily apply
as long as W&B and structural load conditions were met. It was reported as
a one-off ferry flight.

I believe that Peter is rather overly sensitive to say the least.


Thank you for the further info. Even if our opinions differ on this
question, I really would appreciate a pointer to the actual event so I
can look into the difference between my theoretical drag estimates and
some heavy performance data. i

Cheers

"Flaps_50!" wrote in message
...
:
Thank you for the further info. Even if our opinions differ on this
question, I really would appreciate a pointer to the actual event so I
can look into the difference between my theoretical drag estimates and
some heavy performance data. i

I invested 20 minutes of my life in a Google search for a 747
single-engine takeoff and found nothing. I assume that I am not alone but I
also acknowledge that a single search proves nothing one way or another..
Perhaps more importantly, the collective memories of this group have come up
with nothing specific over the last week or two. Until I see a believable
reference, I respectfully choose to believe that it didn't happen.

Vaughn

Aztec crash.
Vr is 70mph. Vmc is 80mph. Vy is 120mph.

The latest article said he knew he had an engine out and was taking
off single engine. Prop wouldn't be feathered because you can't
feather Piper twins on the ground after the engine is dead; you need
800rpm.

Best effort takeoff with 25 degrees flaps, 2 engines, he'd need around
1200' to clear 50' obstacle. No flaps for him because it's too much
drag, so add 50%. Half the engine power is gone, so assuming no loss
to lift, you'd still take twice as long to accelerate. That's 3600'.

What sort of climb should he expect? Best climb at 120mph at sea level
will be about 250fpm. Sub out 50fpm for being 815' MSL Plus 50'
obstacle. Assume he was at 4000lbs and add 150fpm. So, call it 350fpm
at 120mph clean (gear up, prop feathered).

At Vr, he's not going to climb out of ground effect. With gear down,
he's not going to get out of ground effect. With an unfeathered prop
he's not going to get out of ground effect. He's have to hug ground
effect for best acceleration, as pulling up too much would induce too
much drag.

Assuming he had all of that resolved, you'd still have to factor in
the distance to get to a climbing airspeed. Vyse of 120 means he
probably could expect climb performance at about 100 or 105mph. Based
on a whole lot of best case assumptions, you've still chewed up the
entire 5000' runway just to get to some minimum climb speed.

Add in best practices of abort if not climbing by 2/3 down the runway,
and another 25% distance because it's obviously not in new condition,
he shouldn't have attempted such a takeoff, even on a ferry flight,
unless he had 9000' to go with.

Even so, the POH says that if you haven't gotten to within 5mph of
Vyse before the engine fails, that you should abort the takeoff, even
if you're in the air. "Power to idle, land straight ahead."


747 single engine takeoff
Can it fly on 1 engine? Yes. Can it maintain altitude? Maybe. Can
it take off? If it were stripped, light on fuel, maybe.

The Boeing 747 has four turbofans. 4-engine transport category
aircraft are required to demonstrate a 3% positive gradient with an
engine out and gear up.

BEW is about half of MGW on a 747. Parasite drag is 2.2%, and you're
looking at around 150% engine power for climb. But there would be
more induced drag from the rudder pressures, so you might have to
strip the plane and unload 2 of the engine pods. Boeing might also go
past the mins, or use derated engines, so you this might all be
doable. Even so, you'd probably need 5 miles to accelerate to V2.

With passengers, landing fuel, cargo, luggage, SEATS, single engine,
max power, you're still descending.

That's all hypothetical though. A decent flight sim could probably
test this with some model tweaks. AA's sim center could probably test
this. Boeing might have some calculations for this on file somewhere.

On Tue, 15 Sep 2009 19:02:38 -0700 (PDT), JDS Davis wrote in
:

Aztec crash.

... The latest article said he knew he had an engine out and was taking
off single engine. ...

Do you have a link to the latest article?

A reference?

Marty
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