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Ρυμούλκηση

Στο βιβλίο του Dennis Pagen "Towing Aloft", θα βρείτε πολλά και ενδιαφέροντα για το θέμα. Παραθέτουμε στα αγγλικά ένα μέρος του βιβλίου.
Η ρυμούλκηση δεν έχει ευδοκιμήσει στην Ελλάδα. Αυτή την στιγμή [2006] δεν πετά κανείς με αυτό τον τρόπο. Βλέπετε η Ελλάδα μας έχει λίγους κάμπους και πολλά βουνά. Τι να πουν Οι Αυστραλοί και οι Άγγλοι;


 

Tow Phase: Launch process

1. Take up slack (launch observer signals).
2. Apply 2.5 to 7 kg (5 to 15 lbs) to keep the line clear. Pilot inflates glider.
3. Apply 35 to 45 kg (75 to 100 lbs) for liftoff when canopy is up and solid (launch observer signals).
4. Increase pressure as necessary to avoid dropping pilot as the line lifts.

Tow Phase: Climbout

1. As the glider climbs, maintain light tow pressures to above 30 m (100 ft).
2. Gradually increase pressure if necessary to achieve target pressure of 45 to 54 kg (100 to 120 lbs). Normally, pressure must increase to make up for the increasing steepness of the towline. On windy days, even with increased pressure, the effect of the gradient will slow the glider, so the towline pull should be slowed.
3. Be prepared to adjust tow pressure up or down upon receiving a signal from the pilot.
4. Relieve all pressure and/or cut the towline in an emergency.

Tow Phase: Release and Retrieval

1. When the pilot signals or you reach the predetermined tow termination point, reduce pressure for release.
2. Once the pilot has released, reel in the towline with an expedient pressure.

Paraglider Towing Problems

Here we cover what can go wrong and what the crew should look for to determine a course of action. Not every paraglider tow comes off in a picture perfect manner. Here we will look at minor and major mishaps to see how to avoid them or minimize their danger. From Dave Broyles comes a description of what he calls benign launch failures. They are failures in so much as they result in a delayed or aborted tow, but they don't usually lead to an accident with an alert tow crew. In fact, these benign failures are actually successes of the towing procedure if they lead to a safe termination of the tow.

Here is a list of typical problems:

•The canopy fails to come fully overhead.
•The canopy has an entanglement such as a folded tip or a twig in the lines.
•The canopy comes up off center.
•The canopy shoots past the pilot and the front collapses.
•The operator stops because he or she can't see the pilot.
•The release comes loose when the towline first tightens.
•The towline is released below 30 m (100 feet) under conservative tow tensions.

All of these events happen during typical tow operations, especially when the pilot is inexperienced or the conditions are challenging. In all cases, termination or delay of the tow is the proper procedure. If the canopy is not perfectly inflated or positioned as in the first four cases, the launch observer should command "abort, abort" and visually issue the stop signal. The winch or vehicle crew should gently reduce towline tensions and stop launch.
If the tow continues with the canopy well in back of the pilot, the angle of attack will be too high and the glider may continue in a steady state stall (parachutage). The result will be a poor climb rate, lack of control and likely lockout. The same situation can occur during climbout if the pilot uses too much brake control. If the canopy is partially collapsed, it may pull more to the side and lock out. The same is likely to occur if the canopy is not centered. With a frontal deflation, the canopy may horseshoe and the pilot may go for a drag if tow force is increased. If the operator continues towing when he can't see the pilot, any potential lockout could worsen to a drastic stage.
A paraglider pilot is much more dependent upon tow crew decisions for his safety than is a hang glider pilot. A hang glider pilot can release at any time and quickly recover for a safe landing. Unfortunately, abrupt termination of tow forces can be perilous to a paraglider pilot, especially at low altitudes with a canopy trailing far behind him.
Remember that a paraglider pilot cannot readily reduce tow forces during the launch process. He is at the mercy of the tow operator and much force can be deadly.

Dealing with Paragliding Emergencies

The common emergency that occurs when towing paragliders is a lockout. Other emergencies include continuous application of too much brake control, collapse under tow and release failure. In the first three cases, the solution is the same: reduce tow pressure to let the glider regain normal flying status.

Lockout Defense

In the case of lockouts, the tow crew should carefully monitor the canopy for alignment with the towline. If the pilot does not quickly correct a misaligned canopy or if the pilot is below 30 m (100ft), the tow operator should reduce the tow force continuously until the glider responds in the correct direction. Normally, a reduction in the tow force will signal the pilot to pay more attention to the canopy heading.



Oftentimes the canopy in an incipient lockout will not respond to a turn control under full tow force. As long as the canopy is not changing its angle of alignment this force reduction may be gradual. However, if a canopy is rapidly moving away from the towline heading and the pilot is above 30 m (100 feet) the tow force or towline should be cut immediately. An experienced pilot may then bring the canopy back into position and signal visually or by radio to resume the tow. In any case, the only salvation for the pilot during a lockout is a quick reduction in the tow force or a release. It is infinitely better if the tow reduction comes before an uncontrollable lockout occurs.

Canopy Problems

If the pilot is using too much brakes, backing off on tow tension can help bring the canopy above him. The tow crew should monitor the glider for attitude (nose-up position) and pilot position. If the rear of the canopy appears to be less than 3/4 of its normal height above the pilot's head, or wider than a narrow crescent, then either the tow force is too high or the pilot has added brakes, or both may have occured. When viewed from the side, the canopy should not trail back much beyond 45 degrees from the vertical.
When a collapse occurs, promptly but gently reduce the tow force and let the pilot deal with the deflation in a normal manner. Once the canopy has regained its proper flying configuration, the tow can resume upon the proper signal from the pilot.

Release Problems

The tow crew must be especially alert in the event of a release failure. The pilot may be able to communicate verbally that the problem exists, but an alert tow crew should be intently watching the end phase of the tow to see if the pilot stays on line beyond the termination of the tow (the winch or vehicle stops). If so, immediate reduction of tow force is necessary which may include cutting the towline. The tow crew should understand all emergency procedures so they can anticipate what the pilot will do in various emergencies. Stop the tow if things go wrong. Aborted tows slow down the entire operation, but not nearly as much as an accident!

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