Recovery from spin

GRS Rescue ballistic parachute systems (further RS) and their use.
Factors affecting minimum height of using the RS, given by different regulations of testing, consequences arising from different speeds used, eventually passing of aircraft into the spin in its stall speed.In the stated analysis are mentioned ultimate figures of the RS use and their counted figures. As the RS producers of 25-year experience we have encountered with many cases of use in critical situations, which, thanks to the RS, have not ended fatally.Unfortunatelly, we have encountered as well with cases of use similar to those model situations mentioned above. They did not end up in a pub celebration, as in many other happier cases, due to a bad judgement, lack of information and nonacquaintance of the RS proper use.

Each aircraft owner, who decides to purchase and equip his UL aircraft with the RS, should, after consultations with the producer, choose such type and size to comply, along with its technical parameters, with the real weight MTOW limit and the aircraft VNE.

In case the real MTOW, or the VNE, exceeds the technical parameters of the RS, such systém should not be installed and it is adviceable to choose a higher performance RS, even though the RS weight would be bigger.

After the RS installation, the owner should read the manual and parameters of the systems respectively. Producers are obliged to state, by every system, the time of full canopy opening and the speed for which the RS is tested, so that it would be clear, whether it concerns stall speed or other. The producer will state in the manual the minimum height of use according to teh calcualtion of the regulation ZS-2. This complies with the regulations in Czech rep. From this inforamation derives the effective RS use – see the below stated examples.

It is true, that in the USA regulations do not injunct producers to state it on products or in manuals, but production companies are obliged to submit these figures on demand.

There are three norms known in the world under control of state authority for testing the RS

Which are aimed for UL and S-LSA USA.I State here briefly the most important items from regulations.

The Czech republic

Regulation ZS-2LAA CS dated 1.4.1998

  1. Strength tests are carried out at max.speed VNE and maximum take off weight MTOW. The test speed is increased by 1,05 multiple
  2. Oscillation test by descent.
  3. Test of maximum allowed opening time. For 400 kg it is 3 sec. For each further kilogram 0,01 sec is added.
  4. Overshoot test of obstacle 4m long and 2m high towed behind a car at 100km/h –ability to overshoot elevator.
  5. Minimum height of use-test is caried out at the horizontal speed of 60km/h. Time of inflation is recorded and minimum height of use is set. Possible to combine with the item 3.

Along with it, canopy must be inflated at least 2 sec before hitting the ground. The counted minimum rescue height is stated in technical data and announced to the owner.

Example 1: Rescue system GRS 5/472,5 UL. The producer company Galaxy GRS s.r.o.

Input aircraft data: MTOW= 472,5 Kg, VNE =251Km/h
a) Recorded opening time at 45-60 km/h…3,8-3,4 sec.
b) Sinking 6,6m/sec.

Minimum rescue height:

g (weight acceleration) [g = 9.81 m/s2] t ( recorded opening time ) [s] vOP (sinking rate of fully unrolled canopy) [m/s]

At reverse flight + 20 m. Minimum rescue height is then ca: 49,5 + 20= 65m above ground

Conclusion:
The system can be used for the speed of 251Km/h and MTOW 472,5 Kg, or the speed of 260 Km/h and MTOW 450 Kg.

Notice – just to compare rescue system from different producer

Example 2: Rescue system: different producer

Input data:
Recorded opening time at 45 km/h…..8,25 sec.
Sinking rate 6,0 m/sec

Minimum rescue height:

When used at reverse flight (aircraft in upside down position) then to conted height 20 m is added.
Minimum rescue height is then: 178,7 + 20 = 188,7 = ca. 200m (above ground)!!!!

It is 4,5x more than allowed by the regulation LAA ČR and DULV as well! The system must not be allowed to be used in operation.

Example 3: Rescue system GRS 5/560 UL . Producer Galaxy GRS s.r.o.

(This system is for aircraft of higher weight) Input data: Recorded opening time at 65 km/h….. 4,0sec Sinking rate 6,6m/secMinimum rescue height:

At reverse flight + 25 m. Total rescue height ca 53 + 25= 80 m above ground.

Conclusion:
This system can be used for the speed of 250 Km/h and MTOW 560 Kg.

Important notice:
Stated minimum counted rescue heights apply for both systems at horizontal speed and also at spin starting in the stall speed of 65 Km/h.

Germany

Regulation DULV / DAeC dated 30.9.1999 and appendix of 6.9.2006 for other test speeds.
The same as by the LAA CS, but without obstacle overshoot and the weight and speed are not increased by any multiple.
Note: any exceeding of testing limits may result in destruction of user’s parachutes.
Maximum time of canopy inflation must not exceed 4,5 sec. at the speed formerly only 45 km/h, now 65Km/h, 90 km/h till 120Km/h.

Test of using of UL aircraft exceeding max. speed of 190km/h.

This formula applies:

VNE (max. sspeed) [km/h] MTOW ( max.weight- always 472,5 ) [kg]

Example 4: rescue system GRS 6/473 SD UL. Producer Glaxy GRS s.r.o.

Input data:
aircraft weight MTOW = 472,5 kg, speed: VNE = 310 km/h

recorded opening time at 90km/h = 4,5sec
sinking rate = 6,8 m/sec

If the system is used in reverse flight, then to the counted height, 20m is added.
Minimum rescue height is then ca.: 63 + 20 = 83m (over ground)

Notice for spin!
Spins starting at stall speed 65 Km/h.:

Example 5: rescue system GRS 6/473 SD

Here sets in a problem how to determine the minimum rescue height.
Because parachute is tested at the speed higher than the minimum stall speed of UL aircraft (which must not be higher than 65 km/h) higher time delay of inflation occurs in this parachute testing. When falling into spin It is necesarry to add to the tested time at 90km/h, which is 4,5 sec, another ca. 1,5 sec. Then the parachute inflation time will not be 4,5 sec, but 6,0 sec. This does not correspond with the rescue height ca. 63-83m counted, or even tested at the speed of 90 Km/h, but higher by the time to achieve 90km/h. The real rescue height is then higher-see the example:

Minimum rescue height:

If the system is used in reverse flight, then to the counted height, +20m is added.
Minimum rescue height is : 102 + 20 =122m over ground. The difference is then 40 m!

Notice:
We have no input data to compare our system with rescue system from different producer at 300km/h. We have not tested this system. Because the same slider is used, we are convinced that the results for the minimum height of use will be the same as by the previous test from different producer.

Example 6: Rescue system for which will be the opening time up to 4,5 sec at 120km/h
When the test speed is utilized up to 120km/h in 4,5sec. As by different producer, then the minimum rescue height in horizont flight Ho= 83m at 120km/h, but in the spin starting at stall speed 65km/h it is Ho= 173 m above ground! The difference 90m!

It results from the opening time 4,5sec. + 3sec. to achieve 120km/h from the stall speed 65km/h

USA

Regulation: FAA /ASTM F-2316-12 for the category S-LSA: completed

Similar tests as ZS-2 LLA and DULV, but the basic difference is in testing of canopy strength and endurance against load and speed.

  1. Testing speed:factor of cruise speed 200 Km/hx 1,21.Or maximum horizontal speed 222Km/h x 1,1 if the test is performed directly on the airplane.
  2. Maximum take- off weight MTOW x 1,25 if the test is performed directly on the airplane.
    Note: If the test is not carried on the airplane, but by using a concentrated load (dead load) are the weight and speed of the test is recorded and already incorporate coefficients of 1.21 and 1.25 of security, which is ultimately equal to the value of 1.5 safety coefficient.
  3. The total safety multiple for cruise speed is set by the coefficient K = 1,5.
  4. Minimum rescue height. Measured time at stall speed is recorded and announced to user.

Using by the S-LSA in weight of 473 Kg. /GRS 6/473 SD S-LSA/
Min.height of use in spin starting at 90 Km/h – (allowed stall speed for S-LSA) is then the same as for horizontal flight.It is 83 m above ground.
The parachute complies with stated figures of the regulation with safety factor 1,5.

Important notice: when using by UL aircraft, the counted min.rescue height in horizontal flight and spin applies as by the example 5.

Example 7: Rescue system GRS 6/600 SD S-LSA, producer Galaxy GRS s.r.o.

Aircraft weight 600Kg, max.horizontal speed 222 Km/h.
Recorded opening time at 90Km/h …5,8 sec.
Sinking…. 6,9m/sec.

Minimum rescue height:

In reverse flight + 25 m. Total min.rescue height ca…. 125 m over ground.

Applies for the spin and horizontal flight.

Conclusion:
The parachute complies with stated figures of the regulation with safety factor 1,5.

When used by UL aircraft, the counted min. rescue height in horizontal flight is the same as by the LSA.

Important notice:
For spin starting at stall speed 65km/h: 1,5sec is added (from 65 Km/h to 90 Km/h)

Minimum rescue height:

In reverse flight (aircraft in upside down position) +25m is added. Thus the the minimum rescue height in spin is ca.: 145 + 25 = 170m (over ground)

In Liberec 7.11.2008
Ing.Milan Bábovka-Galaxy GRS s.r.o.