So You Want To Fly A Twin Engined Aircraft?

[Karl]

Twin Engines
So You Want To Fly Twins ?
My list of suggestions for success with Twin Engine Aircraft Is easy to understand Don’t Do it unless you’re either mad or have more money than sense.
Rules:
1. Don’t do twins – four times the trouble and worry of a single engine airplane.
2. See number 1.
3. As you can’t follow instructions (you skipped number 2) please read on for my suggestions for success to enter the “exclusive” and challenging world of twin-engine radio controlled model aircraft.
Twin Engine Tips for Success.
Twins are for experienced pilots. Not a second airplane!
Pick a plane where the engines are close together, as this minimises problems during an engine-out situation. DO NOT start with a warbird for a first twin.
Long tail moments and large rudder control surfaces are also a strong advantage to control uneven thrust from two separate engines.
Learn to fly with the rudder! It is very important during take off and for control when an engine out emergency occurs. This is far more important than in single engine airplanes, set for near maximum control deflection.
Pick a tricycle landing gear arrangement. During the take off run, the two engines never come from idle to full speed together. This causes the plane to wonder on take-off far more than you are accustomed to. Tail draggers are much harder to control in twin-engine configuration.

Engine control.
Always bring the engines up slowly on take off to avoid engine out in transition. Do Not immediately firewall the engines. If an engine sags on take off run – do not take off! (Burn this into your brain and remember! it will, save your model).
Never, ever, “tune” the engines for maximum RPM by leaning the mixture. This almost guarantees a dead-engine. Tune them slightly (“more than normal” for a single) rich for increased reliability.
Never lean an engine to match the stronger engine. Yes, one will always be stronger. Richen the strong engine down to the weaker (that is running slightly rich. Remember this way or get the bin bags ready.
Check that idle speeds match and idle mixtures are consistent for reliability and smooth transition to full power.
Most important!!!
 Before take off, always (use a helper if possible for safety) go to full power and hold the plane straight up for 5-10 seconds. Your basic BMFA nose up test But again remember to richen to the weaker engine not richen to the stronger. If you lose an engine at rotate or climb out you will crash!
This is the most vulnerable point in the whole flight. Lose an engine here, and the plane will immediately rollover and spin in. If an engine sags or screams to a lean out RPM – Don’t take off until you correct the problem! My suggestion is to do it once at the pits and again before take off on the runway. Yes, things change from a cold engine to a warm engine. It may work OK in the pit, but lean out on the runway. Do it every time you fly! Engine performance can change as the daytime temperature increases. This can cause lean runs. Idle speeds need to be reliable and reasonably close to the same speed to avoid differential thrust during landing.

Flying Characteristics.
Once you have got to the take off position and have completed all your checks and are perfectly happy Remember this is your last chance to quit if you’re not happy.
(A Trick way for your first twin take-off.) Your first take off with a twin will be less stressful if, after mandatory vertical power check, a helper holds the plane on the runway at full power and releases it at the pilots signal. This eliminates differential thrust during run up at take off. You are already nervous, and this reduces some of the potential problems. If you are starting with a tail dragger this is strongly recommended.)
If everything is good then gently advance the throttle and use the rudder to control the yaw as the engines rise to an even purr remember not to rush this stage as you really want to fly this baby off the field. Gently and as if it is the Mosquito, Beaufighter P38, Me110 or whatever you fancy moving on to.
Remember to turn gently into the circuit using the rudder until you reach the normal 3 mistakes high altitude (yes 3 mistakes high not 2 as is normal for single engine) the plane will fly very similar to single engine airplanes.
You will note the manoeuvres, rolls, turns, etc., require greater input as the wing loading is heavier than a single. The plane feels slightly heavy. Note the wings are heavier due to the greater mass of engines located on them and away form the centre of the fuselage as is normal for single engine airplanes. It takes more force to start and stop this mass.
While you are up here this is the place to get familiar with your model, my suggestion is to slow it to stall the main wing and see the speeds and the models reaction. At this height remember, you should be able to recover safely but again any throttle movement must be smooth and slow. This will lessen the chances of flooding an engine and loosing it (flame out).
Landing (Normal Twin Engine Operation)
Wing loading is higher than standard airplanes (unless it’s a huge un-scale cub style wing) and so landing speeds are faster be prepared for this. Do not try to slow down and risk a stall like a single. The plane is more likely to fall out of the sky than is a single at stall speeds. You have a good idea at this stage of how slow you can go before a stall but remember to err on the side of safety and keep the throttles open a click or two above the stall you have experienced at altitude.
Make your approach with reduced power; not full idle as you would with a single. This will prevent stalls due to low airspeed. It also increases the reliability of the engines because of the slightly higher engine speed. If (and it will happen) an overshoot is necessary, Do not firewall the engines!!! You are near stall speeds and differential thrust at this speed and altitude is very difficult to handle. Lose an engine here and you will crash. Gently bring the engines back up to flying power. Fly straight to gain speed during power up. Climb after engines are at full power.
During power up listen carefully to the engines. Any sagging of one engine means go to idle and land now. Do not risk an engine flame out at landing speeds. Damage from a grass landing and weeds will be less than a high RPM inverted flat spin.
Remember use the rudder, twins are like biplanes, they need rudder to live.
Thought for today.
Taking off with two engines does not guarantee landing with two engines running.  But this can be dealt with Safely without too much sweat.
Single Engine Out Emergency
If possible fly alone as you want to hear the “harmonic” of the two engines. Loss of this sound means trouble, perspiration, elevated pulse, blood pressure trembling hands, etc. Prepare to land NOW!

If flying speed is high, you are relatively safe as control surfaces can control differential thrust. I suggest you pull back power to an absolute high of 75%. With 50% being safer.
Use the rudder!!! If you lose the right engine the plane will yaw and try to turn to the right. Apply left rudder to control yaw. You can apply left aileron to hold the wings level, but you must control yaw or the right wing will stall. Use the rudder! Prepare to land- now! Keep your speed up. Left hand turns are very difficult with the left engine running at high power. If you must turn, I suggest powering back to less than 20% throttle, to reduce differential thrust, and keep the nose down to maintain speed. Make the turn and slowly bring up power if necessary, slowly! No more than 50%. The plane will react as the power comes up, be prepared for it, and prepare to reduce throttle if yaw cannot be controlled. Now use only 50% throttle max as you have lost airspeed and controllability during the turn. Right turns can be made easier than left turns with the left engine running, but the risk of a spin is higher if power is not reduced during turn. Keep the nose down to maintain air speed. Make a normal approach – keep up airspeed. When lined up, cut engine to idle, (this eliminates differential thrust) and land.

On final approach do not bring the power back up. You will crash as airspeed is too low for the rudder to control yaw, use of the ailerons will actually cause the under-powered (Engine out side) wing to stall. This will cause the plane to roll over and dive into the ground. Landing short or long it is always better than an inverted crash. Do not try an overshoot! The slower you fly the less engine power you can use as rudder effectiveness is reduced as air speed reduces.
Twins are definitely fun to fly, draw attention, sound Superb, look COOL, and will demand your best flying skills. REMEMBER never let them see you sweat or shake.
If at any time during single engine flight, yaw increases, a wing rises or you enter a spin, bring the throttles to idle. This will eliminate differential thrust so you can gain control. Lower the nose to gain speed and Land!!! Trying to power up again is very dangerous. You are too slow for single engine control.

Futaba 8 channel, Hitec, and I assume JR all have mixing menus that will allow the two engines to be slaved to the rudder. Example: Right rudder will slow down left engine and increase right engine if below max throttle. This could produce fantastic hammer head turns, reversible spins, easy spin recovery, knife edges etc. I have not tried this…. Yet! But I do suggest you be able to cancel this function very quickly.

More to follow..............

[Sheraz]

Has anyone flown a twin engine yet?

[Gareth]

Yep,

I had no problems, i had a P38 and now phil has it.

Run electric and everything will be fine 

Gareth

[Sheraz]

Yep,

I had no problems, i had a P38 and now phil has it.

Run electric and everything will be fine 

Gareth

ok, one more time,

anyone tried a real twin engine 

[Gareth]

I have a real twin if you want to give it a try.

Its a 3W 70cc flat twin 



Gareth

[Sheraz]

 

Nice!!

[Gareth]

That's some good information, i hadn't thought of it in that way, but thinking about that now it would work perfectly.

Gareth

[TBOY]

Just some input into twin engine flying!  & to correct some of you that are not sure! You shouldn't use more then 5 degrees of bank into the live engine as it makes it worse. The key to a one engine failure is to lower the nose first & apply rudder towards the live engine at the same time, only once you've done these you can then use 5 degrees bank to give back some rudder authority. The main factor is to quickly get airspeed over the rudder to regain rudder authority! Banking is useless without lowering the nose otherwiseby  banking it, it will generate some drag (I'll give anyone a medel if they can bank their model exactly 5 degrees in a twin with one engine out!).  Take my word for it! I fly twins for a living and the first thing I would do naturally & been trained is to lower that nose and get that rudder in, only when i've recovered and stable i'll use 5 degree's of bank to give back some rudder authority cause trust me you'll need it 

[Russ]

Tboy,

I bet you've run through this a few times in the flight sim. How tricky is the landing in this configuration?

[TBOY]

Dave, when i have a chance i will! but to be honest when you fly a 170,200 lb  twin jet for a living the last thing i wanna do is fly Flight Sim & to be honest they don't respond like the real thing. I have done these drills many times in my flying career and having done them recently  as part of my re-currency training.

But saying that I'll try your recipe of doom on the Sim one day - look forward to it 

[andyb]

...The main factor is to quickly get airspeed over the rudder to regain rudder authority! Banking is useless without lowering the nose ...

I've only ever flown single engine motor gliders and the odd Cessna but once you've said that, it makes perfect sense. I read something the other day which basically said that the take-off performance of a twin was governed to a large extent by the ability of the rudder to control an engine failure on takoff - if you're too slow for the rudder to control the yaw resulting from a failed engine, you need to allow sufficient runway to shut own and stop. So a twin usually has a rather higher take-off speed and requires a longer runway than an equivalent single-engine aircraft.

...I'll give anyone a medel if they can bank their model exactly 5 degrees in a twin with one engine out!...

  So I guess the drill with a model is:
1. Lower the nose;
2. Work out which engine's failed;
3. Rudder trim all the way towards the live engine;
4. Keep it as level as possible because we can't tell when there's 5 degrees of bank on;
5. If it looks as though the ground is going to intrude between 1 and 3, throttle back and land where you can.
6. Get into the circuit and land immediately.

Question is, which way should you turn in the circuit? Into or away from the live engine?

A

[TBOY]

If turning towards the dead side the bank should be limited to max 10-15 degrees, so the turn will take alot longer so that's worth considering in the circut for a planned landing. A turn into the Live engine you can bank as normal which is on the safer side.

So this is what I would consider doing on a model twin with a one a engine failure is:

Failure On Take Off:

1. Lower Nose (Quick 1/4 stick forward movement should do the trick)
2. Full Rudder in opposite direction of Yaw
3. Full power very slowly! & correct for Yawing
4. Confirm to your self by saying out load  which engine is dead, this way you will remember! The best way to do this is by saying ' Which rudder input is doing all the work therefore the other side will be you dead engine side'

 ** Example**

Left engine failure!    - Say 'Right Rudder Left engine dead' or for
Right Engine Failure  - say 'Left Rudder Right Engine dead'

5. Apply not more then Half trim (so you will need to fly with constent rudder input) The reason for this is that as you have more airspeed over the rudder the less rudder input you need. The slower you fly i.e. on approach the more rudder input you need. but when landing & you close that throttle remember about that Rudder Trim you left in!!
6. If climb performance is achieved then continue into the circut using nice slow turns. IF not then close throttle slowy & land correct for Yaw changes.
7. Plan your circut & approach using turns into the Live side if possible & decide if you will carry out a landing with one engine or if you prefer to idle the live and carry out a glide approach (treat it as dead stick)
8. Landing - When you are ready to flare remember to retard the throttle and at the same time to ease of the rudder input this will keep the model tracking & flaring in a nice straight line.

Failure in Circut:

1. Lower Nose (Quick 1/4 stick forward movement should do the trick)
2. Full Rudder in opposite direction of Yaw
3. Full power very slowly! & correct for Yawing
4. Confirm to your self by saying out load  which engine is dead, this way you will remember! As above
5. Use trim if needed, but remember not to much or it will mess you up when landing
6. Plan your circut using turns into the Live engine if possible or slow gentle turns into dead engine
7. same as above for Landing - When you are ready to flare remember to retard the throttle and at the same time to ease of the rudder input this will keep the model tracking & flaring in a nice straight line if you decide to carry out the approach with one engine. Or you can close the throttle in the circut and carry out a dead stick approach but remember the glide performance will be crap & don't forget about any rudder trim you left in!

Remember these things & you'll be OK & a confident twin flyer 

Points 3 & 4 are actually the other way around in real life but for Model twins this is ok.

I'm almost convincing myself to finish off my A380 with 4 EDFs!   

[andyb]

I suppose I should admit that I've always had a thing for Mosquitos. Saw "633 Squadron" when I was a kid...

A.

[TBOY]

I agree, They are nice. Just a Vid to intice you 

Break the Bank one!

Jeff Quesenberry's 124" HOLMAN MOSQUITO

Affordable One!

Black Horse DH Mosquito - Electric Twin

[Gareth]

There was a plan in RCM&E a year or so back. I'm sure i can find it to add temptation.

Gareth