More Detailed Frequently Asked Questions
What is actually required, in terms of testing, in the HGMA standards to show that a hang glider meets the standards and is eligible for certification?
There are two classes of tests - flight tests and vehicle tests. The flight tests demonstrate stability, control and performance. The vehicle tests demonstrate stability, especially outside of the normal flight envelope, and structural strength.
Flight Tests:
1) Launch
Successful launch and gliding flight in light winds on a shallow slope, either:
a) Wind of 5 mph or less, on a slope not steeper than 5 to one, or,
b) Wind of 6 mph or less, on a slope not steeper than 6 to one, or,
c) Wind of 7 mph or less, on a slope not steeper than 7 to one.
2) Launch
Successful launch and departure in normal soaring conditions.
3) General maneuvering
General flight maneuvers, showing gliding, diving, turns, slips, stalls, smooth transitions from one flight mode to another, and at least one minute of thermalling flight or other flight in non-uniform air.
4) Spiral stability
Circling turns at 15 to 20 degrees bank in both directions without evidence of significant spiral instability. (Pilot centered on the control bar, or below center).
5) Stall in a turn
Stall in a 30 degree banked turn, slowing at 1 mph per second until stall or full nose up control limit is reached. Recovery to normal flight must be shown, and must occur without excessive loss of altitude, uncontrollable rolling characteristics, or uncontrollable spinning tendencies.
6) Stall straight and level
Stall from level flight, slowing at 1 mph per second until stall results as evidenced by an uncontrollable downward pitching rotation of the glider or full nose up control limit is reached. It should be possible to prevent more than 15 degrees roll or yaw rotation by normal use of the controls throughout this maneuver and the recovery to normal flight, and there should be no uncontrollable tendency for the glider to spin.
7) Spins or spin attempts
Ground based footage must show the pilot making a serious attempt to spin the glider.
If the glider is to be designated as "characteristically incapable of spinning", this must be adequately proven by the documented spin attempts.
Otherwise, the glider must be shown to recover from a spin of x degrees of rotation in not more than half that additional rotation, but in no case in more than 360 degrees of additional rotation without exceeding either the limiting airspeed or the positive limit load factor.
8) Roll Control
The time to reverse a coordinated circling turn at 45 degrees bank angle must be no more than that given by the following equation:
Treq = 4 sec. *( Min. Pilot Wt. / Test Pilot Wt.)
Compliance with this section must be documented using a pilot weight between 1 and 1.5 times the minimum recommended pilot weight. Ground based film footage should show the following sequence:
Glider flies away from camera such that angle of view from camera to glider is not more than 45 degrees above the horizon. Pilot performs one 360 coordinated circling turn at 45 degrees bank, reverses on heading, performs a second 360 degree turn at 45 degrees bank in the opposite direction and then reverses on heading a second time.
Reversals must be initiated within a sufficiently small deviation from the prescribed heading that the bank angle can be adequately judged.
During these maneuvers, the glider should not show dangerous skid characteristics.
9) Steep Dive
The pilot must perform a dive maneuver in which the keel or more appropriate reference makes an angle of at least 75 degrees with the horizon. This dive must be made from a flight maneuver, and airspeeds attained should be observed, recorded and included in the report, although not necessarily filmed.
10) L/D Performance
The L/D of the glider must be at least 5:1. No specific documentation of this performance is required; provided that the film footage, which documents the requirements, listed above is sufficiently indicative of the required performance level.
11) Landing
Ground based film footage must show a safe, controlled approach with turns and landing without the exercise of extraordinary skill. The image of the pilot should be sufficiently large and clear so that the pilot's control movements can be seen.
12) Pitch control authority, Maximum steady state speed, and Static pitch stability and return to trim. (Documented with onboard footage)
a) The pilot must accelerate from a speed of 1.1 times the stall speed to a speed of 1.5 times the stall speed or to 30 mph whichever is greater in no more than four seconds.
b) The pilot must demonstrate the ability to attain and maintain a steady state top speed of at least:
35 mph * (( Test Pilot Wt. / Min. Pilot Wt.)^.5)
c) Maximum steady state speed at maximum loading ( Vdmax ), must be documented if the glider has a maximum steady state top speed, which is less than terminal velocity or less than 120% of Vne.
The maximum steady state speed is computed from the observed steady state speed by:
Vdmax = Vdobserved * (( Max. Pilot Wt. / Test Pilot Wt.)^.5)
d) Onboard film documentation must show that the glider exhibits positive pitch stability over the normal operating speed range: i.e. that it has one specific trim speed, that continuous pressure of the pilot pulling forward (or equivalent) is required to obtain and maintain speeds above trim, that continuous pressure of the pilot pushing back (or equivalent) is required to obtain and maintain speeds below trim, and that the glider returns to trim speed +/- 10% when control pressures are relaxed.
The following maneuvers must be filmed. The camera must show simultaneously the pilot's hands on the control bar and the airspeed indicator. Relative airspeeds must be easily read.
The pilot releases the control bar and allows the glider to establish trim speed. With his hands behind (NOT on top of) the basetube, with open palms so that the only force on the basetube is forward, the pilot pushes out until a speed below trim is achieved. The pilot holds this speed for three seconds, and then by relaxing pressure against the bar allows the glider to return to trim speed.
In a like manner, with his hands open palmed against the front of the basetube, the pilot attains, holds for three seconds, and allows return from at least three speeds above trim, including the maximum steady state top speed. A negative or neutral control force for any speed faster than trim will be considered unacceptable.
Vehicle Tests:
Load Tests:
For a glider with a "typical" maneuvering speed of 46 mph and a never to exceed speed of 53 mph, the following load tests are required. The glider must sustain the required speed for three seconds without failure:
Positive test - at the maximum lift angle of attack, at 65 mph.
Negative test - at a negative 30 degree angle of attack, at 46 mph.
Negative 150 test - at a negative 150 degree angle of attack (tail forward and loaded negatively at 30 degrees), at 32 mph.
A higher maneuvering of VNE speed requires testing to higher speeds. For a glider that, due to its design, cannot sustain the typical VNE speed of 53 mph, testing at slightly lower speeds is permitted.
Pitch Tests:
A test of the glider pitching moment about the pilot tether point, or other suitable reference must be made over the following speeds and angles:
1) 20 mph from 30 degrees above to 25 degrees below zero lift angle.
2) 37 mph from 25 degrees above to 15 degrees below zero lift.
3) 53mph from 10 degrees above to 5 degrees below zero lift.
Vehicle pitching moment tests must be conducted using a "three component" electronic test vehicle, which records two mutually perpendicular resultant components, one pitching moment component, airspeed, and angle of attack in each data cycle, with a minimum sample rate of 2 complete cycles per second. To be acceptable pitch test data must show a smooth angular change with a maximum difference of 2 degrees between consecutive readings.
A graph of the pitching moment coefficient versus the angle of attack shall be plotted for each of the three required speeds from measured forces.
At each of the three speeds, the pitching moment coefficient, when plotted on a graph against the angle of attack relative to zero lift must not enter the shaded regions as defined and shown on the following graphs:
