Motorglider Complexities
When do you shut down or restart your motor?
Motor gliders are great. You take all of the problems and complexity of an airplane then you take the problems and complexity of a glider and put them together... I have been flying a Stemme S10vt since 2000 and no complexity was overlooked.
Flying an ASHEB28
A few things to think about, when you shut down you might not be able to get the engine stowed. So you might be a really bad glider. This year flying PWR an ASH25EB28 we had the centering/brake bearing fail. Eventually, we were able to get the prop stopped and centered, but it took a lot of effort. Later we tried to get it centered after a low restart once we went through the finish cylinder.
We finished, had a downwind against traffic approach possible, however, the tower was not thrilled with that option. So we looked at landing in one of the fields before and below the airport. However, the engine started and we made a full pattern. Eventually, we gave up trying to stow the engine on base and landed with it windmilling, well more turning-over every so often.
Takeoff departure
On the departure, you should treat it like I have mentioned in my aero-tow emergencies article...."You should be surprised when the rope doesn't break" So on a self-launch operation "You should be surprised when the engine doesn't quit."
There are many ways for it to quit. It could run out of fuel, catch on fire, catastrophic failure, pump failure, choke left on, main engine bearing seize, etc.
With the lower climb rate then a towplane many times you can get yourself farther away lower then you would have with a seasoned towpilot who is keeping you within glide of the airport. So just like before releasing from tow you better take a look at the airport and make sure you really want to turn the ignition off. I have a few times continue with the engine cooling to climb a little higher before turning the ignition off.
Stow the engine
Once you get the engine off you have to properly stow the engine and continue with the checklist. One example is when you forget to switch the power supply around you might not be able to get the engine running again. The Stemme can only start from the main battery, it cannot start from the aux battery.
Somewhere in the middle of the Czech Republic, we lost all power in PWR. This wasn't our fault of switches, but an issue with a faulty battery draining all of them together. Anyway, we continued on as a pure glider with a paper map. You can watch our adventure of flying PWR at the CZ WGC here.
Restart the engine
So ignition off and now a pure glider. But hopefully, you will not need to use the engine again. But let's say you do. Did you give yourself enough time to restart it? Can I afford the extra drag to restart the engine? I have had days where I would make the airport but had to land because I was too low to try a restart if it did not restart then I would be landing out. This becomes a factor when having to land off-airport too.
In a pure glider, you would find your field, give up on the soaring, make your pattern and land. Now with the engine, you still need to do that, but you need to include your engine restart into that already established process. So you might need to start at a higher altitude. I am reluctant to say at X height you need to be restarting the engine. But you need to be aware it might not start and you might have to really get lined up for that field landing.
Fly towards your alternate airport or field
Let's say you decide it's time to restart, you are still miles away from home and are getting close to needing to head towards an alternate airport. The first thing I do is head towards the alternate, even if that means turning 180 degrees from home. Once the engine is running I head back on course. However, if you have to do any troubleshooting the glider is still moving towards the airport/fields you can land at. It is very easy to head away, get distracted then not be able to make it to that alternate because you fell below glide.
Engine warm-up period
Remember once the engine is running there might be a warm-up period. With the Rotax engine that could be a while if the engine is cold. Meanwhile, the prop is creating more drag then it was when it was off. So once you get the engine going you might have to keep doing some wandering near the airport and continue to search for lift.
Murphy's law says you will find that thermal once you get the engine started anyway.
Banner photo by Sean Franke
Garret Willat holds a flight instructor rating with over 8000 hours in sailplanes. His parents have owned Sky Sailing Inc. since 1979. He started instructing the day after his 18th birthday. Since then, Garret has represented the US Junior team in 2003 and 2005. He graduated from Embry-Riddle with a bachelor's degree in Professional Aeronautics. Garret represented the US Open Class team in 2008 and 2010 and the Club Class team in 2014. Garret has won 3 US National Championships.