vitek

For those of you who do fly multi engine planes, I have a few questions. If you have a twin, and one engine is out...

1) are you able to taxi around on the ground?
2) should it be possible to get it up to takeoff speed?

If you have some real world experience with this, please supply specifics.

BillS

My Senior Kadet with three engines will not taxi on grass with one outboard running. It might get to takeoff speed with two outboards running but I have not attempted a take off. With bigger engines it might be different.

Attempting to take off with one engine running on a twin would surely be a disaster. Just making descending circles in the air with one running is squirrelly and dangerous to the airframe.

However some people fly in order to build.

If you are looking for one engine out flight experience it would be better to use the radio shut one back to idle at a safe altitude and close enough to dead stick. The technique has worked well for me. Experience in most all engine emergency conditions is being accumulated.

William Robison

My Feedback: (3)

Vitek:

Simple answer, yes, a twin will taxi and fly with a single engine running. More complex answer, with some sport twins single engine flight is trivial, with other models it's almost an impossibility.

My C-3/10 has made a complete flight with a prop on one engine only, with a P-38, B-25, or an F7F I wouldn't even think of trying it.

Bill.

Robby

My Feedback: (18)

vitek,
Lets go into this a little more than what William Robinson did...
The answer to your questions greatly depends on the plane..
Using a simple Stick plane as the GP Big Stik or the H9 Ultra Stick
type of plane.. If you were to have a GP Big Stik 60 and put on
two .60 size motors then yes it would have the power to taxi even
on grass.. Of course, it will or wil want to turn towards the dead motor
constantly making steering difficult..
If flying and motor goes out the plane would have ample to maintain
flight, make turns and depending on experience be manuverable.. Now
take the same plane and put on two .46 motors and the plane will fly well..
It will taxi even on grass but not real well.. When a motor goes out in flight
plane will fly and maintain at level but will want to fall during turns..

Now to address the take off on one motor.. Using the .60 motors it would
be possible to get flying speed up.. Problem is that once plane leaves ground
corrected contoling now is INcorrect for flight and most likely plane will rotate
and go in.. The one with the .46 motors on grass probably would not be able to
reach lift off speed.. On pavement it might but then again, the corrections for
keeping it straight on land will differ from the flight correcttions and the time
it would take for you to do the transition would probably be longer than the time
it took for the plane to go up, and right back down...

Robby

BillS

Bill funny you should mention difficult to fly warbird twins. For a while now I have been searching for a warbird twin Junker to purchase. The intent is to bash it into trainer configuration and learn to fly it. I’m considering stooping very low and adding a center engine for training purposes. Before anyone gets too excited the intent is to remove the center engine after training is complete. The twin disease is hard on the pocketbook.

Maybe something will be found at ‘Warbirds Over Triple Tree’ in Greenville SC next week. Anyone else planning to go to Greenville?

Gremlin Castle

My Feedback: (14)

The design of the plane and the surface from which it is operating have a lot to do with whether it will taxi, or takeoff with one engine.
I have a squint scale F-82 powered by two 25s that will takeoff on one engine if it is on asphalt.
Light wing loading and a good power to weight ratio are the key to reliable single engine performance. Also knowing the VMC of the particular ship helps also.
The referenced plane can be seen in the October Flying Models under the SMALL STEPS coverage.

William Robison

My Feedback: (3)

Vitek:

I suspect Robby is speaking from conjecture, never having done a single engined flight. If your plane has a reasonably low Vmc, not too far higher than the stall speed, you should have no trouble at all.

When you start the take off roll, hold a bit of down elevator and bring the throttle up slowly. As the plane picks up speed add rudder as needed, so long as the front wheel is firmly planted (down elevator) it wont need much. When you're well above Vmc relax the down elevator, and be prepared to add just a touch more (or maybe a lot) of rudder. The plane will come off cleanly, and so long as you don't attempt any radical maneuvers it will fly almost the same as it does with two running, considering the lower power and holding rudder in. Do not let the speed decay, and remember it's safer to turn away from the dead engine. Fly the airplane down final, once you cut the power don't consider going around again.

The Northeast Aerodynamics Twin-Air 40, Dave Platt's Duellist series, or almost any other similar design sport twin is capable of flying on a single engine. Before you try it, I strongly recommend you got some single engine time starting at altitude. It's nowhere nearly as hard as balancing a needle on your fingertip, it just requires smooth control movements and sustained air speed.

Bill.

William Robison

My Feedback: (3)

Vitek:

Just as s side note, there are some full scale twins that can not be taxied, much less taken off, on a single engine. One example is the F7F Tigercat.

Anybody know why?

Bill.

TCBLightning

My Feedback: (5)

When I had my Twinstar I experimented with single engine take offs. The plane was powered by two OS 25 FXs.

Taking off with the left engine was very managable. As Bill described keeping weight on the nose wheel untill you get enough speed definitely helps.

Taking off with the right engine only was a very different story. Very hard to keep going straight. I think it has to do with the torque and p factor both pulling the plane in the same direction. I pulled up on the elevator a little early to get it off the runway and it was very squirrely until more speed was gained. Still a successful flight but a lot of pucker factor!

The 25s are in my twin uproar now (pic is in my gallery). With only 11 inches of separation between the engines it very versatile with one engine.

Twinsanity at it's best!!

Robby

My Feedback: (18)

As vitek ask basic questions my answer was directed in that direction..
As has been noted there are many factors that come into play to determine
the exact answer..
A scale type <especially model> plane will be more difficult that a sport model
plane.. My small Twin Stix has more than enough power for single engine t/o
but the design of the plane it isn't going to happen.. been there, try'd it.. I can
fly it on one engine but do have to work it.. The red GP stick I rebuilt for Toucan
is not capable of single engine t/o on grass but will fly on one engine ok.. Its
a .60 size plane with two .46FX on it..
As TCBLightning noted the Twinstar will do single engine t/o and fly well.. And as
William noted a F7 isn't going to happen, small or large... The answer to Williams
question would be engine spacing being tooo far apart.. The thrust of the engine
being out on the wing so far will over power the ground holding capabilities..
Each plane will have its own characteristics and should be addressed accordingly..
And with practice, each person will have different abilities...

Nowwww, on a side note.. Sometime within the next couple months there will
be a twin ARF on the market.. And within the same time frame there should be
available from another source an 'option package' for the same.. Stayed tuned..

William Robison

My Feedback: (3)

Robby:

The wide engine spacing just makes the F7F more difficult, but that's not why it wont taxi or take off on a single engine. The C-47/DC-3 is another that can't be taxied, and for the same reason as the Tigercat.

Bill.

William Robison

My Feedback: (3)

Robby:

From your "Coming ARF" comment I assume you're still talking to AK?

Bill.

moodier

My Feedback: (1)

Sounds interesting!!Where does the line form?Will be anxious to hear more!Bob Moodie

Robby

My Feedback: (18)

Where as I do talk to AK,, nope...

Hmmm... F7 and C-47/3 has enough power to move on one engine..
But spacing on the Douglas is close and the spacing on F7 is wide..
F7 has rudder out of prop wash but Douglass looks to be in prop wash..

Hmm,, <thinkin' here> .. [sm=idea.gif]

GPaloz

My Feedback: (1)

My guess is that the steering wheel is free castering and the rudder cannot compensate for the off center prop wash. Do I win????????????????? Regards G.

William Robison

My Feedback: (3)

Bill.
You will note I said the C-47 could not be taxied, and didn't mention take off. In theory it could take off on a single engine as the tail wheel can be locked, but I would not want to try it. The Tigercat has caster nose wheel steering with no positive pilot's control, and the C-47 has a fully castering tail wheel. All ground steering on both planes is done with brakes and differential power.

GPaloz wins the brass slug.

Bill.

jimcork1

My Feedback: (4)

Minimum flying airspeed is the definition for the slowest airspeed that will maintain level flight with an engine out.
Usually this also includes rudder and aileron settings and in 4 engine aircraft can also require pulling power on a symetrical engine. What this means to a model is to taxi when you add power from a stop the rudder will probably not have enough air flow to be effective so the nose/tail wheel steering must control direction. Slowly accelerate and maintain directional control with the rudder. The caution here for a model is you don't know your MCS (Minimun Control Speed) because you don't have an airspeed indicator. If you lift off early before the rudder has enough throw to control yaw,, you will crash. The key here is to accelerate slowly, transition from nose wheel to rudder control, then lift off at the highest airspeed you can get. After lift off bank into the good engine might be necessary and turns into the good engine after takeoff almost manditory. Do not turn into the dead engine after take off. Once stabalized flying at a high enough airspeed altitude you can try to turn into the dead engine but watch for loss of control. If this occurs, pull back power and regain control then add power and pull out of the dive.

Good discussion Ya' have fun.. Jim

jamesg33

My Duelist will not even taxi with just one engine going - it just spins around. There's not enough weight on the nose gear to provide the turning ability to handle the asymmetric thrust. Happens on grass or pavement.

I programmed all of my Duelist's parameters into my Realflight sim and amazingly, it won't taxi on one engine either! Just spins around like the real thing.

Jim

vitek

You guys are awesome. I don't fly planes, it is just something that I have been wondering about. One of those things that might not translate perfectly from full scale aircraft.

Thanks!