Hi Roger,
Hope she is repairable.
Twin engined models are just like twin engined real airplanes. They have a speed at which below they can no longer maintain directional control.
In the real airplane it is called VMC. In the older WWII airplanes it was called "takeoff safety speed". In the B-25, that I flew in airshows, it is 145 mph. The airplane breaks ground on take off at 90 mph. So for a period of time it is in a vulnerable position, this is called the "critical area". During this climb in the "critical area", a shallow climb angle is used to accelerate as quickly as possible to 145 mph, and during this period the gear is raised and both pilots check over their shoulder to look at the engine cowls and vertical fin for oil, a great indicator for impending failure.
If the engine fails below 145 mph, with the rudder pushed all the way to the stops, and the wings rolled to the perfect bank into the running engine, the airplane will still turn and roll into the failed engine and eventually the nose will drop. The airplane is out of control. The only way to save ones self in this condition is to reduce power on the running engine, usually to idle, and prepare to land, wings level, straight ahead. To continue with the power up on the good engine below VMC, close to the ground, will be an impact with terra firma in an out of control state. Usually it is very bad.
Now for a twin engined C/L model, we have some options after an engine failure too. We have a model that has a VMC too, but it usually is accelerated past very quickly. The airplane turns at us a little bit more than a single engine job on take off because of torque from the two engines, but because of the quick acceleration, no sweat. Take a step back and all is well.
When we have an outboard engine quit on the twin, the inboard engine is producing thrust from the inboard side of the model's vertical axis and trying to fly it against the control lines and away from the pilot. That is good, a little help from our engine. In this case, one can fly it pretty well. It slows down, and if you'll notice, you can fly it up higher than your head, maybe up to a little higher circle elevation, like eight feet, but it is very thrust critical. But it has line tension so we feel safe.
Now, if the inboard engine quits, the model will have the opposite reaction, it will try to turn in towards the pilot, making the lines slack, while slowing down and becoming thrust critical. One must immediately step back and maintain line tension.
How do we save it? By walking in a tight backwards circle and keeping a constant tension on the lines. Whipping, or in racing, towing, is something that used to be taught to everyone , but nowadys I see a lot of guys aren't really up on it. Essentially, you are walking away from the model, producing line tension in a circle just like the model is flying in. This produces energy to the model, keeping the lines tight and providing control effectiveness.
Remember when the model would barely fly higher than your head with the outboard engine stopped? Well, now is a good time to fly nice and low. Lower than your head, and maybe it won't even stay airborne, depending on the model.
Try these things, and I hope this stuff helps you give it a go again. I love to see twins and scale models even more.
Chris...
Topic: b-25 in the ground (Read 837 times)