Introduction
Glider pilots train for abnormal and emergency procedures in case of control problems, instrument failures, or equipment
malfunctions. In addition, since forced landings may occur due to inadequate lift on a cross-country flight, glider pilots
should understand how to use emergency equipment and survival gear as a practical necessity.
Aerotow Abnormal & Emergency Procedures
Environmental factors, pilot error, and mechanical equipment failure can cause an abnormality during aerotow. The tow
and glider pilots should avoid situations that would place the other pilot at risk. Should a situation arise where the glider
position threatens the safety of the tow plane, the glider pilot may have no other choice but to release the tow rope.
Environmental Factors
Environmental factors for terminating the tow include encountering clouds, mountain rotors (area of turbulence created by
wind and mountainous terrain), or restricted visibility. Any of these factors may require the glider pilot to release.
Pilot Error
Examples of tow-pilot errors include starting the takeoff before the glider pilot gives the ready signal, using steep
banks during the aerotow without prior consent of the glider pilot, or frivolous use of aerotow signals, such as “release
immediately!” For the glider pilot, examples of pilot error include allowing the glider to get out of position during the tow,
losing sight of the towplane, or leaving air brakes open during takeoff and climb.
Kiting
A hazardous situation may occur during takeoff if the glider pilot flies high above and loses sight of the towplane. If the
tension on the tow line pulls the towplane tail up, the tow pilot may run out of up-elevator authority. In addition to a the
towplane experiencing a nose down pitching moment, it is also loosing airspeed. The kiting glider creates a huge amount
of drag which slows the towplane. It can take 1,500 feet or more for the towplane to recover once the rope breaks or the
glider pilot releases.
Unintended Spoiler Deployment
Spoiler-related emergencies often result from a pilot’s failure to lock the spoilers in the closed position prior to takeoff.
As the glider accelerates down the runway, or soon after it becomes airborne, the airflow deploys the spoilers, greatly
increasing the glider’s drag. The pilot may not notice the spoilers open, but the increased drag can make it impossible
for the tow pilot to climb and clear obstacles. A release by the tow pilot leaves the glider low to the ground and in a high
drag configuration. If the glider pilot does not recognize the situation, and close the spoilers, an unsafe landing becomes
likely. If conditions permit a continued climb the towpilot can waggle the rudder to indicate something is wrong with the
glider. The glider pilot should differentiate between the towpilot rocking the wings indicating release immediately, and the
towpilot fanning the rudder indicating something is wrong with the glider, avoiding an unnecessary release.
If time allows, the tow pilot can use the radio and warn the glider pilot to close the spoilers. Without using radio, the tow
pilot can use the “Rudder Waggle” signal for the glider pilot to check the glider. The glider pilot should not confuse this
signal with the “Wing Rock” signal for the glider pilot to release the tow rope. This mistake would leave the glider pilot at
low altitude with the spoilers open and make a safe landing very difficult.
Chapter 8: Abnormal & Emergency
Procedures
Mechanical Failures
Mechanical equipment failures include tow hook failures, towplane mechanical or airframe failures, and glider airframe
failures. The tow pilot rocks the wings of the towplane to request an immediate release by the glider pilot. [Figure 8-1 right
panel] The glider pilot may deliberately terminate the tow or launch anytime it seems safer than continuing. For example,
if the glider pilot discovers control binding once air pressure builds on the surfaces, releasing the tow line seems less risky
than continuing. If a mechanical failure occurs, the glider pilot should assess the situation and determine the best course
of action. Options include remaining on the aerotow, planning to release at a point in the future, or releasing immediately.
Glider: Release immediately
Towplane rocks wings
Glider cannot release
Glider moves to left side of towplane
and rocks wings
Towplane cannot release
After receiving signal that
glider cannot release,
towplane yaws repeatedly
Figure 8-1. Towplane and glider signals due to release mechanism failure (left and center panels) and towplane signal commanding
glider release (right panel).
blank
Tow release failure can occur in either the towplane or the glider tow hook system. If the glider release mechanism fails,
the glider pilot should notify the tow pilot either by radio or tow signal as depicted in the left panel of Figure 8-1 above,
and the glider should maintain the high tow position. The tow pilot should tow the glider over the gliderport or airport
and release the glider from the towplane. The towline should fall back and below the glider. The design of some tow hook
mechanisms allows the line to pull free from the glider by its own weight. After release by the towplane and since some
glider hooks do not back release, the glider pilot should pull the release to increase the likelihood of a towline release from
the glider. In the rare event the tow pilot also cannot release, the tow pilot will yaw the tow plane repeatedly as shown in
the enter panel of Figure 8-1 above.
tow planes often use a variant of the Schweizer or Tost glider tow hitch. [Figure 8-2] and [Figure 8-3] The hitch connects
to the tow plane fuselage below the rudder. The specific rings that attach tow lines to these hitch types can be seen in
Figure 8-4. The wing runner should know the correct method of attachment. If the tow plane has the Schweizer tow hitch,
the tow ring may rotate forward and trap the sleeve that locks the tow hitch in place if the glider flies too far above the tow
plane during the tow. This may prevent the tow pilot from releasing the tow line. [Figure 8-5]
Towhook closed
Towhook open
Figure 8-2. A Schweizer tow hitch.
Ring
Hook
Figure 8-3. A Tost tow hitch.
Schweizer ring
Tost ring
Figure 8-4. Examples of Schweizer and Tost tow rings.
Excessive pressure here
Tow ring
Pilot can not override
excessive pressure with
cockpit release handle.
Tow hook pulled up
Glider excessively
high on tow
Figure 8-5 A Schweizer tow hitch under upward tension.
Failure of the release mechanism in both towplane and glider occurs very rarely. If it does occur, radio or tow signals
between glider pilot and tow pilot should confirm the situation. One option has the glider and towplane landing without
releasing from one another. Once a descent to the gliderport or airport begins in this scenario, the glider pilot should move
to and maintain the low-tow position and use spoilers/dive brakes to avoid overtaking the towplane. The tow pilot should
plan a shallow approach that avoids obstacles and allows the glider to touch down first. The towplane could experience a
hard landing if the glider pilot uses the wheel brake excessively and slows the towplane below its flying speed. The glider
pilot should use the spoilers or dive brakes to stay on the runway and use the wheel brake only as necessary to avoid
overtaking the towplane.
A second option in a dual release failure situation involves the glider pilot breaking the towline while within gliding
distance of the landing field; however, using this slack-line procedure increases risk of entanglement and could damage
the glider or towplane if the line does not break as designed. The pilot flies the glider above the towplane, dives down to
develop slackline, and then fully extends the dive brakes and/or spoilers to induce a tension overload. As the towplane
accelerates without the load of the glider and the glider decelerates due to the increase in drag, the towline should come
under sudden tension and break free. If the glider pilot cannot verify that the line break occurred at the glider's weak link,
the glider pilot should land using the landing procedure for an attached line in the GFM/POH.
The following sections discuss five tow failure situations for which a pilot should have a plan. While the best course of
action depends on many variables, such as runway length, airport environment, density altitude, and wind, all tow failures
or emergency releases have one thing in common: the need to maintain control of the glider. For example, the pilot should
avoid stalling the glider or dragging a wingtip on the ground during a low altitude turn.
Tow Failure with Sufficient Runway To Land and Stop
If a tow failure or deliberate release occurs prior to towplane lift-off, the towplane either continues the takeoff or aborts the
takeoff. If the towplane aborts the takeoff, the tow pilot should maneuver the towplane to the left side of the runway. For
a glider still on the runway, the glider pilot should pull the release, decelerate using the wheel brake, and maneuver to the
right side of the runway. If the glider becomes airborne, the glider pilot should pull the towline release, land ahead, and be
prepared to maneuver to the right side of the runway. [Figure 8-6, panel 1] Pulling the towline release in either case ensures
that the rope remains clear of the glider. Since local procedures vary, both the glider pilot and tow pilot should know any
specific gliderport or airport procedures.
Very low altitude, premature release/
rope break with runway still available.
Land on runway, use wheel brake to
stop. If necessary, alter course to the
right to avoid towplane.
Very low altitude, premature release/
rope break with insufficient runway
available. Land ahead, use wheel break
to stop.
Wind
800 feet above the runway, if suitable,
turn into the wind for course reversal,
land downwind.
Above 200 feet, if suitable, turn into wind and
make course reversal, land downwind.
Wind
Figure 8-6. Situations for tow line break, uncommanded release, or power loss of the towplane.
Tow Failure after Takeoff—Glider Unable to Return to Airport
When an inadvertent release, tow line break, or a signal to release from the towplane occurs at a point at which the glider
has neither sufficient runway directly ahead to land nor sufficient altitude (typically 200 feet above ground level) to make
a safe turn back to the field, the pilot should land the glider ahead. [Figure 8-6, panel 2] Glider pilots should consider any
attempt to turn at low altitude prior to landing as high risk because of the likelihood of dragging a wingtip on the ground
or stalling the glider. Landing ahead and slowing the glider as much as possible prior to touchdown and rolling onto
unfamiliar terrain often provides the best outcome. Low speed means low impact forces, which reduce the likelihood of
pilot injury or damage to the glider. Glider pilots should look on both sides and ahead when choosing the best area for an
off-field landing. While more altitude provides more range during an emergency, landing under control supersedes getting
to a “perfect” landing area almost within glide distance.
Tow Failure above Return to Runway Altitude
A glider pilot may consider and attempt a downwind landing on the departure runway if the glider possesses sufficient
altitude to make a course reversal. [Figure 8-6, panel 3]
The pilot should only attempt a course reversal and downwind landing option if within gliding distance of the airport or
landing area. In ideal conditions, this maneuver typically requires a minimum altitude of 200 feet above ground level. If
there are strong headwinds, the pilot should consider that the glider will reach 200 feet AGL with less distance traveled
across the ground. This may allow for landing-ahead options on the existing runway compared to reversing course, landing
with less return runway available, at a considerably higher groundspeed, and possibly risking overshooting the entire
runway on return.
The glider pilot has responsibility to avoid the towplane if the tow terminates due to a towplane emergency. Since, the tow
pilot deals with that emergency and may maneuver the aircraft abruptly, the glider pilot should never follow the towplane
down.
After releasing from the towplane at low altitude and if the glider pilot chooses to make a turn of approximately 180°
for a downwind landing, the pilot should maintain flying speed. The pilot should immediately lower the nose to a pitch
attitude that maintains the appropriate airspeed. If a rope break occurred, the glider pilot should release the rope portion
still attached to the glider to avoid any entanglement.
During a course reversal, the pilot should make the initial turn into any crosswind using a 45° bank angle. This bank angle
provides a safe margin above stall speed, incurs an acceptable amount of altitude loss, and completes a course reversal
in a timely manner. Using a shallow bank angle may not allow enough time for the glider to align with the landing area.
An excessively steep bank angle may result in an accelerated stall or wingtip ground contact. Provided the departure
drifted downwind and the pilot makes the turn back to the field into the crosswind, the glider may only need minor
additional course corrections to align with the intended landing area. Throughout the maneuver, the pilot should maintain
the appropriate approach speed and proper coordination to maximize range.
While downwind landings result in higher groundspeeds, the glider pilot should maintain the appropriate approach airspeed.
Landing downwind results in a shallower than normal approach, and the pilot may use spoilers or dive brakes to control
the descent path during the straight-in portion of the approach. Higher groundspeed becomes especially noticeable during
the flare. After touchdown, the pilot should use the spoilers or dive brakes and use wheel brakes to slow and stop the glider
before any loss of directional control. During the latter part of the roll-out, the glider may feel unresponsive to the controls
even though rolling along the runway at a higher than normal groundspeed.
Tow Failure above 800' AGL
When the emergency occurs at or above 800 feet above the ground, the glider pilot has more time to assess the situation.
Depending on the gliderport or airport environment, the pilot may choose to land on a cross runway, into the wind on the
departure runway, or on a taxiway. [Figure 8-6, panel 4] In some situations, an off-gliderport or off-airport landing may be
safer than attempting to land on the gliderport or airport.
Tow Failure above Traffic Pattern Altitude
If an emergency occurs above the traffic pattern altitude, the glider pilot should maneuver away from the towplane, and
release the tow line if still attached. The glider pilot should turn toward the gliderport or airport while evaluating the
situation and then decide whether to search for lift or make an immediate return to the gliderport or airport for landing.
Pilots should remember their obligation when dropping objects (such as a tow line) from an aircraft according to Title 14
of the Code of Federal Regulations part 91, section 91.15, and not create a hazard to persons and property on the ground.
[Figure 8-12, panel 4]
Slack Line
Slack line is a reduction of tension in the tow line. If the slack is severe enough, it might entangle the glider or cause
damage to the glider or towplane. The following situations may result in a slack line:
• Abrupt power reduction by the towplane
• Aerotow descents
• Glider turns inside the towplane turn radius [Figure 8-7]
• Updrafts and downdrafts
• Abrupt recovery from a wake box corner position
• Glider dives toward towplane [Figure 8-8]
Glider turns toward inside of
towplane turn. Glider slows,
slack towline develops.
Figure 8-7. Glider bank steeper than that of towplane, causing slack in tow line.