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1. 06:00 AM - Limit Load Ratings and their effects (Thom Riddle)
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Subject: | Limit Load Ratings and their effects |
--> Allegro-List message posted by: "Thom Riddle" <jtriddle@adelphia.net>
Paul at Aero-Siam brought to my attention something that should probably be posted
here about Limit Load ratings. The Allegro is rated at 4.0+ and 2.0- Gs at
a flying weight of 520 kg or 1,146 lb. In the USA, the Allegros have a gross
weight limit of 1,232 lb. so the pilot/operator must be aware that if flying above
the 1,146 lb. Limit Load Rating weight the actual limit loads must be adjusted
downward for the additional weight.
At 1,232 lb. the flying weight is 7.5% heavier than the rated Limit Load weight
of 1,146 lb. The ACTUAL LIMIT LOADS for the Allegro flying at 1,232 lb. will
be 3.7+ / 1.9- Gs, not the 4.0+/2.0- in the Allegro documentation. These numbers
are derived by dividing the 4.0 and 2.0 by 1.075, the increased weight factor.
ALSO, be aware that the LANDING GEAR may be designed for a MTOW of 1,146 lb. and
operating at 1,232 lb. should be done with caution, particularly in landing
operations, to avoid undue stress in the landing gear and associated components.
A hard landing at 1,146 lb. may be sustainable but the same rough landing at
1,232 lb. might cause cracks or failure of the landing gear.
The Stall Speeds are also affected by flying weight but not by the same factor.
The Allegro manual says the Calibrated Airspeeds at stall for the three flap
positions were taken at 1,146 lb., as follows:
FLAP 0 43 knots or 49.5 mph
FLAP 1 39 knots or 44.9 mph
FLAP 2 35 knots or 40.3 mph
Since LIFT is a function of the square of airspeed the increase in weight to 1,232
lb. (7.5% increase) does not affect the stall speed by this amount. It affects
it by the square root of this increase, 1.075
.5 = 1.037
The Calibrated airspeeds at 1,232 lb. should be as follows:
FLAP 0 44.59 knots or 51.3 mph
FLAP 1 40.44 knots or 46.5 mph
FLAP 2 36.30 knots or 41.7 mph
Thom in Buffalo
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=11819#11819
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