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Jeff Goin

 
 

DULV Certification Process

Sept 14, 2007 by Jeff Goin with input from Pons Lars of Swing and German pilot Stefan Obenauer

Here is some clarification on DULV paraglider testing.

First, tests are flown using a paramotor as opposed to free flight without a motor. They are flown at the wing makers listed maximum take-off weight and include tests with trimmers closed and open if the glider is equipped with trimmers.

We are checking to see if they do tests with speedbar on those gliders so equipped.

Here are some aspects of the DULV testing. Remember, this is only required in Germany but the testing can provide valuable information to wing buyers.

1. The glider must have a minimum wing load of 9.9 lbs/m� (4.5 kg) to be considered a motor glider, otherwise it's a motor-assisted paraglider (like a powered sailplane). In Germany, motor wings with a lighter loading must have both and DHV certification. The philosophy is that a smaller glider is more stable, faster and has less tendency to negative spin (a Cessna doesn't have wings like a glider).

2. Load test to insure the glider is structurally able to handle the extra load imposed by heavier weights typical of their use.

3. Maneuvers have been adapted especially to the paramotoring purpose. Here is some of what is tested by the DULV. Some of the highly dynamic tests are flown in free flight for test-pilot safety.

  • launching behavior
  • level flight with no oscillation allowed (see sidebar on this, though)
  • multiple turnarounds / sharp turns. (no collapse allowed; must not have any tendency to negative spin).
  • flying under full power (must not have any tendency to deepstall or full stall; brake travel has to be long enough to do a turn against the torque effect).
  • Pulling brakes until glider wants to enter the full stall (glider must signal the full stall, have progressive brake pressure and sufficient brake travel).
  • front stall in the worst condition - no thrust.
  • one side collapse in the worst condition - no thrust.
  • spiral dive (glider must not accelerate).
  • full throttle - idle - full throttle - idle (no front stall or collapse allowed).
  • landing behavior.

4. main difference between DULV Standard and DULV Advanced is that, if you want to gain the Standard certificate, the glider has to recover on its own without active piloting.

The Naja is the first (and only as of 9/14/2007) wing to be certified advanced.

Difference From DHV

The DHV tests wings only using a standard harness with set riser spread. DULV tests wings in combination with a motor as a set and tests to see that a wing is generally suitable for paramotoring. In Germany, the glider has to be tested with every single engine, a process simplified by doing only a conformity check flight. The merely insures that the wing has no unusual behaviors when flown with that particular motor.

So a complete test is flown under one motor and a comformity test flown with other motors that want to be certified with that wing. That is probably where the misconception comes from about DULV only doing one flight with a motor.

Jason Shapiro flying along with an induced 50% collapse.

Motor-wing Oscillation

Some wings, when combined with some motors, will oscillate. You swing back and forth in shallow little banks with no pilot input.

It is caused by the motor twisting slightly at the end of an oscillation. The thrustline turns to point the other way and pushes in the other direction, causing it to worsen slowly.

I see this behavior in about 5% of the wings I try and it has never been more than annoying for hands-off cruising.

Another pilot, on a different motor (even the same brand), may not experience the tendency.

If your motor twists when the risers are lifted unevenly than it is subject to having this happen.


Remember, If there's air there, it should be flown in!