In addition to the standard flight control systems found on all gliders, self-launching gliders have multiple systems to support flight under power. These systems may include but are not limited to the following:
- Fuel tanks, lines, and pumps
- Engine and/or propeller extension and retraction systems
- Electrical system including engine starter system
- Lubricating oil system
- Engine cooling system
- Engine throttle controls
- Propeller blade pitch controls
- Engine monitoring instruments and systems
The complexity of these systems demands thorough familiarity with the GFM/POH for the self-launching glider being flown. Any malfunction of these systems can make it impossible to resume powered flight.
Self-Launching/Sustainer Glider Engine Failure During Takeoff or Climb
Engine failures are the most obvious source of equipment malfunction in self-launching gliders. Engine failures can be subtle (a very slight power loss at full throttle) or catastrophic and sudden (engine crankshaft failing during a full-power takeoff). High on the list of possible causes of power problems are fuel contamination and exhaustion.
To provide adequate power, the engine system must have fuel and ignition, as well as adequate cooling and lubrication. Full power operation is compromised if any of these requirements is not satisfied. Monitor the engine temperature, oil pressure, fuel pressure, and revolutions per minute (rpm) carefully to ensure engine performance is not compromised. Warning signs of impending difficulty include excessively high engine temperatures, abnormal engine oil temperatures, low oil pressure, low rpm despite high throttle settings, low fuel pressure, and erratic engine operation (surging, backfiring, and missing). Abnormal engine performance may be a precursor to complete engine failure. Even if total engine failure does not occur, operation with an engine that cannot produce full power translates into an inability to climb or perhaps an inability to hold altitude despite application of full throttle. The best course of action, if airborne, is to make a precautionary landing first and then discover the source of the trouble.
Regardless of the type of engine failure, the pilot’s first responsibility is to maintain flying airspeed and adequate control of the glider. If power failure occurs, lower the nose as necessary to maintain adequate airspeed. Pilots flying self-launching gliders with a pod-mounted external engine above the fuselage need to lower the nose much more aggressively in the event of total power loss than those with an engine mounted in the nose. In the former, the thrust of the engine during full power operations tends to provide a nose-down pitching moment. If power fails, the nose-down pitching moment disappears and is replaced by a nose-up pitching moment due to the substantial parasite drag of the engine pod high above the longitudinal axis of the fuselage. Considerable forward motion on the control stick may be required to maintain flying airspeed. If altitude is low, there is not enough time to stow the engine and reduce the drag that it creates. Land the glider with the engine extended. Glide ratio in this configuration is poor due to the drag of the extended engine and propeller. The authoritative source for information regarding the correct sequence of pilot actions in the event of power failure is contained in the GFM/POH. The pilot must be thoroughly familiar with its contents to operate a self-launching glider safely.
If the power failure occurs during launch or climb, time to maneuver may be limited. Concentrate on flying the glider and selecting a suitable landing area. Remember that the high drag configuration of the glider may limit the distance of the glide without power. Keep turns to a minimum and land the glider as safely as possible. Do not try to restart the engine while at very low altitude because it distracts from the primary task of maintaining flying airspeed and making a safe precautionary landing. Even if power in the engine system were restored, chances are that full power is not available. The problem that caused the power interruption in the first place is not likely to solve itself while trying to maneuver from low altitude and climb out under full power. If the problem recurs, as it is likely to do, the pilot may place the glider low over unlandable terrain with limited gliding range and little or no engine power to continue the flight. Even if the engine continues to provide limited power, flight with partial power may quickly put the glider in a position in which the pilot is unable to clear obstacles, such as wires, poles, hangars, or nearby terrain. If a full power takeoff or climb is interrupted by power loss, it is best to make a precautionary landing. The pilot can sort out the power system problems after returning safely to the ground.
Inability to Restart a Self-Launching/Sustainer Glider Engine While Airborne
Power loss during takeoff roll or climb are serious problems, but they are not the only types of problems that may confront the pilot of a self-launching glider. Other engine failures include an engine that refuses to start in response to airborne start attempts. This is a serious problem if the terrain below is unsuitable for a safe off-field landing.
One of the great advantages of the self-launching glider is having the option to terminate a soaring flight by starting the engine and flying to an airport/gliderport for landing. Nearly all self-launching gliders have a procedure designed to start the engine while airborne. This procedure would be most valuable during a soaring flight with engine off during which the soaring conditions have weakened. The prospect of starting the engine and flying home safely is ideal under such conditions.
As a precaution, an airborne engine start should be attempted at an altitude high enough that, if a malfunction occurs, there is sufficient time to take corrective action. If the engine fails to start promptly, or fails to start at all, there may be little time to plan for a safe landing. If there is no landable area below, then failure to start the engine results in an emergency off-field landing in unsuitable terrain. Glider damage and personal injury may result. To avoid these dangers, selflaunching glider pilots should never allow themselves to get into a situation that can only be resolved by starting the engine and flying up and away. It is best to keep a landable field always within easy gliding range.
There are many reasons that a self-launching glider engine may fail to start or fail to provide full power in response to efforts to resume full power operations while airborne. These include lack of fuel or ignition, low engine temperature due to cold soak, low battery output due to low temperatures or battery exhaustion, fuel vapor lock, lack of propeller response to blade pitch controls, and other factors. It is important for the pilot to have an emergency plan in the event that full engine power is not available during any phase of flight.