Aircraft Crash Survival Analysis and Design
Return completed exam to instructor by 10:00 PM on 11 December 2012. Send to email:
Provide an essay type answer for the following questions.
1. Describe the effect plowing can have on crash forces when the impact surface is soft soil.
Earth gouging and scooping of soil occur when the structure makes initial contact with the ground which minimize the acceleration and force levels to which the structure is subjected. Soft soil can cause plowing and rapid deceleration if there is a large horizontal velocity component. A high-speed longitudinal impact into water can also cause high loads from water plowing as water enters through lower nose transparencies. Reducing the earth scooping effects encountered in longitudinal impacts should include a large, relatively flat surface thereby increasing the aircraft's tendency to slide over the impact terrain and by minimizing inward buckling of the fuselage nose or engine nacelle to maintain skid surface integrity.
2. Explain the term submarining in respect to the use of lap belt restraints. What human injuries may result?
This is where the lap belt rides over the pelvic brim and compresses the soft tissues of the abdomen resulting in serious abdominal and spinal injuries. Submarining occurs due to the pelvis rotating under the lap belt, usually due to inappropriate location of the lap belt anchors or due to poor design of the seat bottom or a combination of both. Lap belt only restraints so commonly inflicted serious injuries on users in automobile crashes that the medical community coined a new term, “the seat belt syndrome”, to describe the constellation of injuries caused by submarining under the lap belt. ftp://ftp.rta.nato.int/pubfulltext/RTO/EN/RTO-EN-HFM-113/EN-HFM-113-06.pdf
3. Discuss forward and rearward facing passenger seats and explain which you feel may be an advantage in crash survivability.
The rearward-facing seat is optimal for providing maximum support and contact area in longitudinal impacts. The only critical impact sequence for the rearward-facing seat is one that involves a severe lateral component that allows sideward movement of the occupant prior to application of the longitudinal or vertical Pulse. However, lateral torso movement can be minimized by use of a torso restraint system of much lighter weight than that required for other seat orientations. The rearward-facing cabin seat is preferred.
4. Explain the concept and intention of Delethalization of Cockpit and Cabin Interiors.
The delethalization of cockpit and cabin interiors is the design and set up of aircraft cockpits and cabins to prevent injury on impact. This is done by ensuring the occupant's immediate environment be designed so that when the body parts do flail and contact rigid or semi-rigid structures, injury potential is minimized. This can be done in different manners. First is to relocate the hazardous structure or object out of the occupant's reach or the hazard might be reduced by mounting the offending structure on frangible or energy-absorbing supports and applying a padding material to distribute the contact force over a larger area on the body member.
The aircraft interior has occupant strike envelopes, meaning that there are hazards that are more conducive to occupant injury than others. Overall the intent is to protect the head and torso first to prevent debilitating injuries or death and then protecting the lower body parts to ensure the area hazards are clear of tripping hazards or anything that could prevent rapid escape. Typical contact hazards in the cockpit area include window and door frames, consoles, controls and control columns, seat backs, electrical junction boxes, glare shields, and instrument panels. Contact hazards commonly found in aircraft cabin areas include window and door frames, seats, and fuselage structure. Use of suitable energy...