Posted Thursday, April 1, 2010 @ 11:06 AM
I am putting Patrick's info here that he had addeded to the EAA article, since it is interesting in its own right.
Ray
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The question of G Load limit has often beeen raised in the Fournier forums.
Early editions of the RF4D Pilot's Handbook clearly quote +6/-3g at aerobatic weight.
In an official accident report I found the following statement :
G-loads RF5
The LBA-BFU (German Civil Aviation Authority-Accident Investigation Board) accident report ref. 3X 956-092 (crash of a RF5 Callsign: D-KIFD on 8. April 1992) contains some concrete details on page 10 about the G-Load limits of the RF5 wing. Please refer to the annex with the original text in German .
This RF5 had an in-flight structural failure while performing aerobatics near Frankfurt, with 2 pilots on board. The flight conditions were marginal, and the air turbulent on that day.
This particular RF5 had been involved in several damages on the ground, but had always been repaired and inspected at the manufacturers factory.
Here a tentative translation, because this is a difficult text .
In the wing load tests documented by the manufacturer, the numbers indicate that the recovery load, (A1) at a speed of 204 kmh (CAS) is 6 G. This is the maximum stress that the main wing can safely be subjected to.
During the calculations of the wing spar’s flexibility regarding the bending moment, the rigidity of the fir spars were determined as 84 N/ mm2 during expansion and 42 N/mm2 for compression, until material failure occurs..
It was found that even at the weakest point of the wing ie. 25 % of the half wing, (which corresponds to the approximate position of rib 18), and using a safety margin of 1,5 there was still an approx. + 4 % reserve before failure would occur.
Using the information from the case study above,The airworthiness requirements for TMG’s (Touring Motor Gliders) require a minimum wing G-Load of + 5,3 without cumulatively adding wind gusts loads.
My deduction :
Minimum wing loading requirement for a motor glider is a G-load of + 5,3
The RF5 has been stress tested and designed for a G Load of + 6 G (recovery at 204 kmh).
A safety margin of 1,5 has been taken into consideration.
This means the total possible load factor is 6 x 1,5 = + 9 G before structural failure occurs.
Patrick Faucheron , Germany 21.3 2010
[Edit by jb92563 on Thursday, April 1, 2010 @ 11:30 AM]
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