asymmetry must be overcome or eliminated. One way to  solve this problem is to deploy the other spoiler/dive brake  to restore the symmetry. The advantages include immediate  relief from yaw and roll tendencies and protection against  stalling with one spoiler/dive brake extended and the other  retracted, which could result in a spin. The disadvantage of  deploying the other spoiler/dive brake is that the glide ratio  is reduced. If the spoiler/dive brake asymmetry arises during  launch or climb, the best choice is to abort the launch, extend  the other spoiler/dive brakes to relieve the asymmetry, and  make a precautionary or emergency landing. Environmental factors include low temperature or icing  during long, high altitude flights, which may occur during a  mountain wave flight. Low temperature causes contraction  of all glider components. If the contraction is uneven, the  spoilers/dive brakes may bind and be difficult or impossible to  deploy. Icing can also interfere with operation of the spoilers/ dive brakes. High temperature, on the other hand, causes all  glider components to expand. If the expansion is uneven,  the spoilers/dive brakes may bind in the closed position.  This is most likely to occur while the glider is parked on the  ground in direct summer sunlight. The heating can be very  intense, particularly for a glider with wings painted a color  other than reflective white. Mechanical failures can cause asymmetrical spoiler/dive brake  extension. For example, the spoiler/dive brake extend normally  during the prelanding checklist but only one spoiler/dive brake  retracts on command. The other spoiler/dive brake remains  extended, due perhaps to a broken weld in the spoiler/dive  brake actuator mechanism, a defective control connector, or  other mechanical failure. The glider yaws and banks toward  the wing with the extended spoiler/dive brake. Aileron and  rudder are required to counteract these tendencies. To eliminate  any possibility of entering a stall/spin, maintain a safe margin  above stall airspeed. If the decision to deploy the other spoiler/ dive brake is made to relieve the asymmetry, controlling the  glider becomes much easier but gliding range is reduced due to  the additional drag of the second spoiler/dive brake. This may  be a significant concern if the terrain is not ideal for landing the  glider. Nevertheless, it is better to make a controlled landing,  even in less than ideal terrain, than it is to stall or spin. Towhooks can malfunction as can any other mechanical  device. Failure modes include uncommanded towline release  and failure to release on command. Pilots must be prepared  to abort any towed launch, whether ground or aerotow  launch, at any time. Uncommanded towline release must be  anticipated prior to every launch. Assess the wind and the  airport environment, and then form an emergency plan prior  to launch. If the towhook fails to release on command, try to  release the towline again after removing tension from the line.  Pull the release handle multiple times under varying conditions  of towline tension. If the towline still cannot release, alert the  towpilot and follow the emergency procedures described in  Chapter 7, Flight Maneuvers and Traffic Patterns. Oxygen is essential for flight safety at high altitude. If there  is a suspected or detected failure in any component of the  oxygen system, descend immediately to an altitude at which  supplemental oxygen is not essential for continued safe  flight. Remember, the first sign of oxygen deprivation is a  sensation of apparent well-being. Problem-solving capability  is diminished. If the pilot has been deprived of sufficient  oxygen, even for a short interval, critical thinking capability  has been compromised. Do not be lulled into thinking that  the flight can safely continue at high altitude. Descend  immediately and breathe normally at these lower altitudes for  a time to restore critical oxygen to the bloodstream. Try to  avoid hyperventilation, which prolongs the diminished critical  thinking capability. Give enough time to recover critical  thinking capability before attempting an approach and landing. Some gliders are equipped with a drogue chute to add drag  during the approach to land. This drag supplements the drag  provided by the spoilers/dive brakes. The drogue chute is  packed and stowed in the aft tip (tail cone) of the fuselage or  in a special compartment in the base of the rudder. Drogue  chutes are very effective when deployed properly and make  steep approaches possible. The drogue chute is deployed and  jettisoned on pilot command, such as would be necessary if  the drag of the glider was so great that the glider would not  otherwise have the range to make it to the spot of intended  landing. There are several failure modes for drogue chutes.  If it deploys accidentally or inadvertently during the launch,  the rate of climb seriously degrades and it must be jettisoned.  During the approach to land, an improperly packed or damp  drogue chute may fail to deploy on command. If this happens,  use the rudder to sideslip for a moment, or use the rudder  to yaw the tail back and forth. Make certain to attain safe  flying speed before attempting the slip or yawing motion.  Either technique increases the drag force on the drogue chute  compartment that pulls the parachute out of the compartment. If neither technique deploys the drogue chute, the drogue  canopy may deploy at a later time during the approach  without further control input from the pilot. This results in  a considerable increase in drag. If this happens, be prepared  to jettison the drogue chute immediately if sufficient altitude  to glide to the intended landing spot has not been reached. 8-25 Miscellaneous Flight System  Malfunctions Towhook Malfunctions Drogue Chute Malfunctions Oxygen System Malfunctions