By Thomas Knauff

Many things can go wrong during the beginning of a glider launch. Most people immediately think of a rope break, but there are numerous emergency situations. A recent article listed 42 possible emergencies during the first few seconds of a launch.

When a group of experienced pilots were asked to list possible emergencies, few thought of a canopy opening on tow. As it turns out, many accidents occur as the result of an inadvertent canopy opening. These accidents resulted in damaged gliders and even the death of one or more of the occupants of the glider or tow plane.

When a canopy opens suddenly, surprise is probably the immediate reaction, causing the pilot to react improperly and possibly losing control of the glider. The sudden rush of air and the accompanying noise can be very disturbing. If the glider happens to be a two-place glider and the passenger becomes excited, this will add a further distraction for the pilot.

Glider Canopies

There are four common canopy installations. Some gliders have a canopy that is removed so the pilot can get in or out. Other popular canopy systems include side opening, forward hinging, and rearward hinging. Some two-place gliders have both a forward hinging and a rearward-hinging canopy.

When a removable canopy or a rearward hinging canopy is left unlatched, it typically departs the glider very suddenly. An unlatched canopy may give a slight warning before opening. The warning can be an unfamiliar hissing wind noise or a rattle as the canopy dances against the frame. Sideward hinging canopies usually have a lanyard to allow them to be left opened while the pilot enters or exits the glider. Front hinging canopies, although sometimes difficult to jettison in an emergency, are probably the safest from the standpoint of this discussion as when left unlocked, they typically lift up slightly, but are kept mostly closed by the air loads of the slipstream.

In all cases, the glider flies just fine without the canopy. It is noisy. If the pilot wears glasses, the wind can blow them from the pilot’s face, so vision can be greatly impaired. A spare set of glasses can be stored in a pocket for such an emergency. Wind in the pilot’s eyes will cause tears to flow and it can be hard to breath.

It is possible for a jettisoned canopy to damage the tail of the glider, but it is rare for the damage to cause a complete loss of control. It is also possible for the canopy to strike the head of the pilot or passenger, which can cause injury or unconsciousness.

A canopy opening on tow is very serious, and it happens often enough for all pilots to be aware of the problem. Pilots need specific training including preventative plans of action to prevent the problem and exercise a good plan of action when it does occur.

Prevention

The best plan of action is to exercise procedures to prevent the problem in the first place. Carefully using a pre-takeoff checklist is extremely important. The checklist must be performed without interruption or distraction from bystanders. While a pilot is preparing for takeoff, bystanders must be made to stand aside and be quiet. The wing runner should be trained to help the pilot by insisting on quiet and asking people to stand well clear.

The wing runner can also be trained to observe the pilot performing the pre-takeoff checklist. Is the tail dolly removed, are the flaps in a logical position, did the pilot perform a positive control check and critical assembly check? Is the area in front of the tow plane clear of bystanders or other obstructions? Does the tow plane appear and sound to be in good working order? Is the tow rope OK? Is the canopy or canopies closed and locked?

Other alert pilots in the immediate area can also play an important role by simply being alert to common launching emergencies. Almost everyone watches as a glider is preparing for launch. It only takes a slight increase in awareness by everyone nearby to become actively involved.

Gliders and tow planes should be encouraged to have radios and to use them. The tow pilot can ask the glider pilot, “Dive brakes and canopy locked?” The tow pilot can be trained to watch for common pilot errors such as a canopy unlocked, tail dolly still on, dive brakes unlocked, and the new CAC (Critical Assembly Check) mark on the left wing tape.

Maintenance

The canopy latching mechanism needs to be cleaned and lubricated from time to time. Grob sailplane canopies use the rubber seal as an integral part of the latching mechanism. If the rubber seal is worn out, the canopy will close so the canopy frame and the fuselage opening will bump together. The opening mechanism will unlatch easily. The canopy frame should press firmly against the rubber seal. The seal must be replaced on a routine basis.

Other gliders use springs or friction locks to secure the latching mechanism once it is in the closed position. Some people have installed additional Velcro straps to hold the handle closed.

When a canopy does open on tow, the canopy hinges are sometimes bent, cracked or broken. A distorted hinge may cause the latching mechanism to be misaligned so it does not function properly. A careful inspection should reveal any problems and repairs made before the next flight.

What to Do

Despite all these efforts, pilots will still take off with an unlocked canopy. As the glider rolls along the runway a small bump or gust of air might cause the canopy to vibrate. Often, there is an unfamiliar whistle of air or a bumping noise as the canopy rattles against the frame.

A well-trained pilot will expect this, as well as other emergencies, and recognize the problem immediately. With lots of runway remaining, the obvious plan of action is to release and roll to a stop.

If the glider is airborne with inadequate runway to land straight ahead, the pilot of a side-opening canopy can press on the appropriate rudder to sideslip the glider. The resulting airflow will keep the canopy closed.

The pilot of a front-hinged canopy simply accepts the error, increased noise and windy cockpit and continues the tow to a safe altitude before releasing.

The rearward opening or removable canopy gliders will experience very little warning before the canopy is gone.

The Left Hand

Gliders are normally flown with the right hand. The left hand is used to pull the release knob, adjust flap settings and elevator trim.

During the beginning of the tow, the pilot should have the left hand near, but not on the release knob in case of an early emergency such as a tow plane engine failure.

Another common emergency is for unlocked dive brakes to open as the wings begin to generate lift. The pilot should be alert to this possibility and be prepared to hold the dive brake in a closed position.

Finally, the pilot must expect the canopy to open sometime in a flying career, and be prepared to grab the canopy frame to keep it closed. The warning, if any, will be very brief and perhaps impossible to respond quickly enough, but there is a chance. During this attempt, the pilot must maintain the proper towing position and not allow the glider to move out of the normal tow position.

There is a risk if the pilot has the left hand near the canopy release mechanism at the beginning of the tow. A firm bump can cause the hand to lift up and possibly unlatch the canopy. Passengers should be warned to keep their hands well clear of the canopy mechanism.

Plans of action:

Front hinged canopy gliders – accept the error and continue the tow to normal release altitude without trying to latch the canopy while on tow.

Side hinge canopy gliders ­– press on the appropriate rudder to sideslip the glider. Hold canopy closed with left hand. Tow to normal release height before attempting to latch canopy.

Rear hinged canopy gliders – Only chance is to try to grab canopy frame.

In all cases, the pilot’s primary responsibility is to maintain control of the glider and maintain proper position on tow.

Canopy Blows Off

Should this happen, it will be very noisy with a lot of wind. Common aero tow speeds are 70 mph or more. Your hat will be gone, perhaps your glasses too.

Try ducking down so the instrument panel shields your face. Protect your face and eyes with your left hand until you reach release altitude. If it is a two-place glider, the rear pilot may be able to fly easier than the front pilot. Conversation will be near impossible.

If possible, radio the tow plane pilot of your problem. It may not be possible to hear your radio. Make more than one transmission. People on the ground will also hear your predicament and will clear the runway.

On side hinged canopy gliders, the canopy will probably open fully, break the restraining cable and lie against the fuselage. The glider flies just fine. Stall speed only increases by a couple of knots. Even the reduced glide ratio is not a major consideration. Fly the glider at the normal pattern airspeed to reduce noise and wind. Fly a normal landing pattern using the dive brakes or flaps to land slightly longer than usual into the runway.

After release, it may be possible to latch the canopy, but don’t make too much effort. It is far more important to continue to fly the glider and maintain control.

As in many emergencies on tow, the pilot’s first responsibility is to continue to fly the glider. A canopy opening on tow should be nothing more than an embarrassing event.