Introduction
Airframe Designs was tasked by STC Twenty One to complete a bird strike substantiation assessment on a Cobham SATCOM HGA-7000 antenna. This antenna is typically located on a BOEING 757-200 aircraft. This was done to to show the FAA and EASA that the antenna meets the requirements to be a discrete source of damage as per the original certification basis requirements.
The aircraft must be able to complete a flight where structural damage is likely to occur due to the impact of a 4 pound bird at operating speeds at 8000 feet. The assessment identifies the antennas critical features and determines the areas which are most likely to fail.
Bird Impact Loading
An assessment was required to find the static strength Reserve Factors (RFs) for quasi-static strength and quantify the level of conservatism included within the assessment. An empirical formula from RAE paper TR72056 was used to calculate the impact force acting on the antenna:
F=1.18M^(2/3) V^2 Cosα
Where:
F = Force normal to the impacted plane
M= Mass of the Bird
V=Impact velocity
α = Impact angle
Overall Risk Assessment
In addition to the strength calculations for the bird impact force, quantitively assessments also considered:
- The probability of bird strikes based on the size and location of the antenna compared to the aerodynamic boundary layer and the flying altitude of the aircraft.
- The number of installations of the antenna on aircraft and the type of aircraft they are installed onto including the years of service.
- Antenna/ fuselage materials, construction and the means of attachment of the components.
- Ability of the radome to experience a discrete penetration during impact but retain the ability to hold stagnation pressure.
Through detailed Analysis, AFD showcased exceptional technical expertise and skill, delivering a high standard for the customer. Click the link to read the full case study.
www.airframedesigns.com/portfolio/boeing-757-antenna-installation-bird-strike-substantiation/
Click the link below to discuss how we may be able to help with your bespoke engineering challenges.