Re-starting an engine in flight if the propellor stops
Reading the latest Australian Flying magazine where its flight safety correspondent Jim Davies discussed engine power loss in flight. Each aircraft POH normally publishes an emergency checklist to cover this sort of thing.
Lack of fuel (dry tank) is the usual culprit. One subject that I haven't seen addressed in single engine trainers is where the propeller stops while the aircraft is gliding or during the lead up to practice stall recovery. It was quite common to see this happen in Tiger Moths during aerobatics where the only method to re-start was to dive steeply to force the prop to rotate again. In fact this was part of RAAF training in Tiger Moth days. Part of the pre-aerobatic check was to ensure a suitable forced landing field was within gliding distance.
For what it's worth I thought the following experience might be handy reading for instructor course candidates flying Cessna 152 or 172.
I was teaching a new student how to fly gliding turns just off the coast near Point Cook. We started around 3000 ft and all went well until around 1500 feet I sensed the prop was windmilling more slowly than normal.
I told the student to start climbing but as I said the words the prop stopped and we were forced to resume gliding again. I sent out a quick Mayday on the local frequency and again on an ATC frequency besides squawking 7700.
Trying the starter motor didn't get the engine running so I had to reach over to the student's far side to get to the primer and tried two shots then the starter. We were down to 800 feet and I had already planned to ditch alongside some boats 200 yards off shore. The nearby sports oval at the mouth of the Werribee River was too far away for comfort.
The primer worked, the engine started, Maydays were cancelled and we landed back at Point Cook normally. We were down to around 500 feet when the engine started.
The maintenance release was clean except for one earlier endorsement which had been rectified. What we didn't know was the same aircraft did the same thing to another instructor a few days earlier while on stalling practice in the training area at 3000 ft. In this case the instructor dived the Cessna and got the prop turning again. He refrained from writing up the defect in the maintenance release. That omission nearly cost us wet feet.
A few weeks earlier I had flown the same aircraft and found the primer plunger was hard to operate and on the verge of seizing. Turned out it had been like that for months but not written up.
In the case of our incident it was a stroke of luck that I had endorsed the faulty primer in the maintenance release and it was repaired otherwise we may not have been able to operate the primer plunger when the prop stopped and been forced to ditch. Reluctance to endorse defects in the maintenance release for fear of upsetting someone is a well known problem in GA. Maybe not nowadays but common decades ago. It could save the life of the next person to fly that aircraft.
For flying instructors faced with a stopped prop during training sequences it is worth considering a quick pump of the primer and then start rather than diving and risk losing valuable altitude if it doesn't work.