Managing Flying Risk – Motorgliders, self launching, and self-sustainer sailplanes
This page includes guidance on:
- Operations in general
- Mixed operations
- Wet wings
- Fuel management
- Carburettor icing
- Field landing training
- FES ground safety
- Self-Launching and Self-Sustainer Sailplane Airborne Engine Start
- Training for Self-Sustainer Sailplane Airborne Engine Start
- Single Seat De-Regulated (SSDR) aircraft
Operations in general
Motor gliders are usually fairly simple aircraft with few mechanical things to go wrong. But when things do go wrong, there is rarely a backup system waiting to take over. Many, including those with VW derived engines have only one ignition system, which like all things mechanical, will not last forever. Regular servicing is essential, but so is recognition by pilots that failure is possible, which will result in a forced landing for which they should be prepared. So what can we do to mitigate the risk and avoid breaking the motor glider?
An engine failure after take-off is an obvious risk area, especially so until the aircraft is high enough to return to the airfield. Consideration should be given to landing options during climb out. It may be that the club is winching in a particular direction which is less suitable for motor glider (or aero tow) operation. A different take-off direction might be negotiated. In any event, the pre departure brief (eventualities) is essential. Fields should be picked until the aircraft is in a position to return to the airfield. It might be the magneto partially fails, giving a reduced rate of climb. Carburettor icing might have the same effect. Planning beforehand is always better than trying to make a plan after the engine has malfunctioned.
Those of a certain age may remember a placard which was common in many aircraft. It went something like ‘This aircraft must not be operated in such a way that an engine failure would result in a hazardous situation.’ Planning so that an engine failure results in nothing more serious than a field landing is the aim. Ask yourself ‘do I really need to fly over that big built up town, or moorland, or mountain, or other unlandable area? What are the landing options?’ The best way to answer those questions is to stay in practice, ideally with a suitably qualified instructor.
Guidance on operating a mixed gliding and motor gliding/self-launching sailplane operation is included in the “Motor Glider Handbook” on the BGA website. A key issue here is maintaining adequate separation between cables/ropes and motor gliders.
Most motorgliders and self-launching sailplanes use a wing section that is sensitive to rain. Accumulated rainwater on the wings and the tailplane will in most cases negatively impact take-off performance and handling. Please refer to the Pilot Operating Handbook. In all cases, snow or ice should be removed before takeoff.
It is the pilot in command responsibility to ensure that an aircraft does not run out of fuel in flight. Aircraft fuel gauges are in general only certified as accurate when showing empty. The following good practices can help busy pilots and instructors;
- Careful physical checking of fuel contents before flight – a calibrated dipstick may be useful
- Checklists or mnemonics used before, during and between flights or tows that require a check of “fuel contents”
- Assume a higher than flight manual figure for fuel consumption and plan (eg x/litres per tow) to finally land with enough fuel to deal with unforeseen circumstances. The Law requires pilots to have reserves.
- Regular checking of fuel gauges during maintenance
Carburettor icing has existed as long as powered aircraft. Carburettor heat where fitted should be used as described in the aircraft flight manual. The lower the power setting, the greater the risk of carburettor icing.
A prolonged descent (for example during motor glider field landing training) will very likely result in a cool exhaust manifold and insufficient heat may be available to clear any ice if hot air is selected. This may be alleviated to an extent by use of hot air during the final part of the previous climb while at a high power setting. Whether a carburettor hot air system is fitted or not, assurance that the engine will respond to throttle movement should be carried out during the descent by occasionally and briefly demanding high power at heights that would enable the aircraft to make a successful forced landing in the chosen or adjacent fields should the engine fail to respond adequately.
Field landing training
Field landing training is most usefully provided utilising a Toring Motor Glider (TMG). While realism is desirable in any training context, the overriding consideration should always be the safety and legality of the flight.
The Rules of the Air state that aircraft should not fly closer than 500’ to any person, structure, vehicle, or vessel, unless landing or taking off normally. Field landing training, and indeed simulated engine failure after take-off, does not qualify as normal aircraft operation and is therefore subject to the rule. It is worth noting that if an aircraft goes below 500’ in an apparently remote area, and a person out of sight behind a hedge is approached within 500’, the aircraft captain is potentially liable to prosecution. If animals are present in the area, they may be frightened by the sudden appearance of a MG even if it is above 500’. This in turn may give a landowner reason to start legal action.
Most MGs do not have the safety of twin magnetos or electronic ignition. All suffer to some degree from carburettor icing, whether or not they are fitted with a carburettor heater. Before even starting a descent, instructors should ensure that the carburettor is clear of ice by early use of the carburettor heater, and that the oil temperature is well above the minimum specified by the manufacturer. The carburettor heater should be used throughout the descent, and oil temperature monitored. A small amount of power should be continually used to keep the engine warm and to simulate the performance of the glider. An occasional application of full power will ensure a response is available. This response check is essential around the base leg. If the engine does not behave normally at this point, the exercise should be terminated and the instructor should land in the chosen field. The go around must be planned in such a way that an engine failure on climb out also results in a successful field landing.
Threat and Error Management
Field landing in gliders always carries a higher risk than landing on an airfield. Training for field landing in MGs carries a similar, but often higher risk factor as there are more things to consider for an instructor, and more opportunities to make mistakes. Risk increases exponentially as height is lost, particularly if the exercise is continued below 500’. A normal glider circuit descends through 500’ somewhere between low key and base leg. As soon as the base leg is commenced, it should be obvious to both instructor and student whether the approach will be successful, so there is very little reason to continue lower, into the high risk area. EVEN WHERE LEGAL, LOW APPROACHES CARRY TOO HIGH A RISK TO BE JUSTIFIED ON TRAINING GROUNDS. If a student cannot successfully fly the approach, the airfield is the right environment for remedial action. With more experienced pilots practicing field approaches, the exercise can usually be abandoned at low key or earlier as the selection is likely to be the major learning point for them.
The CFI should ensure that instructors teaching field landings maintain their competency in the exercise.
FES Ground Safety
FES equipped gliders are relatively new and unfamiliar to other airfield users who may not appreciate the dangers of the flush seated, self deploying, fast turning and solid propeller blades on the nose of the glider. In addition to any precautions described in the aircraft flight manual, these points can be helpful:
Whether or not you fly a FES equipped glider, always treat a FES propeller as ‘live’.
Insist that helpers or onlookers always keep clear of the propeller.
Tow out with the motor disarmed, eg the key removed if there is one, and any prop-guard in-place.
Don’t touch the FES switches when anyone is near the front of the glider.
People are interested in new technology. Don’t allow them to ‘fiddle’ with the FES switches.
If taking an aerotow or winch launch in a FES equipped glider, make a point of advising those hooking-on of the FES installation and insist that they approach the hook from behind the cockpit to keep clear of the propeller and its potential arc of travel.
If self-launching in a FES equipped glider, keep the canopy open until you are have completed your pre-flight checks and are ready to start, then loudly call “clear prop” before closing the canopy.
If someone helps with ground handling after landing a FES equipped glider, make a point of advising them of the FES installation and to remain clear of the propeller and its potential arc of travel.
As a FES operator, consider how you can minimise the risk to others on the ground, including by disconnecting the batteries.
Self-Launching and Self-Sustainer Sailplane Airborne Engine Start
Self-launching and self-sustainer sailplanes are equipped to assist their pilots in staying airborne. A well-maintained engine system, a practiced pilot and a sensible operating protocol usually results in a safe and timely engine start and climb. Accident report data indicates that most problems occur due to a late decision to start the engine.
There are several important considerations, including:
Practice & familiarization
- Older engine/prop systems can require complex starting procedures. Become familiar with all starting ‘drills’ while sat on the ground.
- Please refer to the flight manual.
- In some cases where multiple actions are needed to erect and start the engine, in flight pre-positioning of selectors and switches may be appropriate and helpful. Some operators use a numbering system to help to ensure multiple actions are addressed in the correct order.
- In many cases the engine/prop produce significant drag and therefore steepen the glide angle. This is less of an issue with jet and FES installations. Please read the flight manual.
- Wing loading (water-ballast) can be a limiting factor in safely achieving the (low) speed needed to retract or extend the engine/prop. Please read the flight manual.
- The deployed engine can affect the glider’s handling and stability. Read the flight manual and explore at altitude the effects both with the engine running and with the prop stationary.
- Practicing engine/prop deployment and starting before needing to use the system during a cross-country flight is important. Some operators practice landing at their home airfield with the engine/prop deployed but not running to get used to the changed performance and in some cases changed handling. Circuit planning needs careful attention.
- Having a pre-considered and personally agreed minimum height for engine start – effectively a pilot’s own ‘red line’ – is very important. The flight manual will provide guidance. Determine how much height you lose deploying and starting the engine and hence decide a sensible decision height. Recognize that descending beneath this height effectively discards the engine option.
- Dive starting will consume more height, and must therefore be begun earlier, than a well-practiced electric start.
- Checking fuel and batteries should be part of the daily inspection.
- Carrying out an engine start each time before leaving safe gliding distance from the home airfield will prove the system and refresh the pilot’s ability to use it.
- It is important to accept that a conventional field landing will happen if a pilot’s minimum height for starting has been reached before deploying the engine.
- As should always be the case when flying cross-country, constantly monitor the available landing options. Have a landing option selected before deploying the engine/prop.
- When a decision has been made to deploy and start the engine/prop, the priority is to fly the glider.
- While the engine/prop is deploying, keep flying the glider and stay aware of the chosen safe land out option.
- When the engine starts, again keep flying the glider (the flight manual should describe the best climb speed and profile – eg climb-cruise) and stay aware of positioning relative to the chosen land out option.
- If the engine does not start, keep flying the glider and prepare to land out on the chosen land out option. Only if there is time/height to do so, logically check for a reason for non-starting, eg fuel and ignition, before another start attempt while continuing to fly the aircraft towards the safe land out option
- Recognize that deploying and using the engine adds to pilot workload and potential distraction in an already busy stage of the flight. Being in practice and starting the engine in good time will reduce stress and reduce the opportunity for human errors to occur.
Training for Self-Sustainer Sailplane Airborne Engine Start
Pilots may choose to receive some flight training on the use of the self-sustainer system fitted to their glider. A two-seat glider fitted with a self-sustainer engine is one option. However, as few two-seat turbo gliders are available, simulating the use of a self-sustainer when flying a TMG is another option. Any TMG gliding instructor who has questions about simulating the use of self-sustainer in a TMG can contact the BGA.
Whether or not two-seat training is available, the Aircraft Flight Manual, the guidance at ‘Practice & familiarization’ above, and advice from experienced self-sustainer pilots (especially those who are also instructors) will be helpful.
Single Seat De-Regulated (SSDR) aircraft
There are very few formal requirements surrounding SSDR’s. They are freed from the burden of airworthiness regulation because they pose negligible risk to third parties. However, they are not required to be designed and built to the same standard or have the same level of crashworthiness as conventionally designed CS22 sailplanes and powered sailplanes. The fact that there is no legal requirement for design evaluation, maintenance or flight testing does not mean that these should not be done. It is entirely up to the owner to decide on his or her own approach to these activities; BGA inspectors can provide guidance to owners.
Licencing and medical requirements apply. Flight training for self-launching privileges is likely to take place in a TMG. Launch type training and conversion guidance applicable to pilots of all self-launching sailplanes including SSDR’s is available here and is recommended to all new pilots of self-launching sailplanes including SSDR’s. BGA instructors can provide guidance.
Guidance specific to the Silent 2 Electro
Test flying of a Silent 2 Electro in support of an accident investigation has identified several features associated with the type that pilots may not be aware of:
- Very light stick forces in pitch combined with high levels of friction in the controls. This means the pilot receives minimal feedback on how the aircraft is responding to control inputs. Flying with a more forward cg should increase stability and stick forces.
- Very little physical or aural indication that a stall is approaching with full power. Practising power-on stalls at a safe height can teach the pilot how to recognise the subtle indications of an approach to a stall with full power (and with other power settings).
- Indicated airspeed can increase erroneously during and post stall when full power is set.
- Self-launching with Flap 0 instead of Flap +1 (Flap +1 is recommended in the flight manual) may be helpful. There is very little difference in stall speed between Flap 0 and Flap +1, but the trim speed is higher with Flap 0, which means that there is a higher trim margin to stall. The angle of climb will be shallower with Flap 0.
- The flight manual does not provide a take-off or climb speed. A climb speed of 50 kts provides normal handling and should ensure a good margin to stall.
- Take-off technique. Keeping the tailwheel on the ground, or just above it, until lift-off reduces the chance of a propeller strike. Aggressive use of large forward stick inputs early in the ground run should be avoided, particularly on uneven surfaces, as this increases the likelihood of overcontrolling in pitch and a prop strike.
- Procedure for an aborted take-off. Cutting the power quickly using the FES rotary knob is not as easy or as intuitive as pulling back on a throttle lever (for example in a TMG). Pilots should on all occasions complete a comprehensive self-brief for the take-off and any eventualities. This should always contain a point on the take-off run where the acceleration of the aircraft can be checked. Pilots should mentally rehearse what they would do in the event of needing to abort a take-off to be able to correctly react to a problem.
- Weight & balance. The weight and balance tables for one aircraft seem to be using a moment arm for the nose ballast that is 10 cm greater than the physical distance measured. This would mean that the W&B tables are indicating a more forward CG than reality.