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Boeing 737 AD

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posted on Sep, 15 2009 @ 02:46 PM
The FAA is releasing an Airworthiness Directive aimed at operators of Boeing 737-300, -400, and -500 operators after a Southwest Airlines incident in July. The flight was going from Nashville to Baltimore, and made an emergency landing in Charleston, West Virginia with a 17 inch hole (43cm x 20cm) in the upper rear fuselage between two stringers.

This is an eerily similar (yet safer) incident to Aloha 243 in Hawaii on April 28, 1988 (a 737-200). A passenger boarding the aircraft noticed a crack in the fuselage, which during flight opened and tore the top of the aircraft off, at 24,000 feet while they were South-Southwest of the island of Maui. It's now believed that the flight attendant that was killed (C.B. Lansing) was pulled into the hole, and blocked it, causing a pressure increase that tore the top of the plane off. This added to corrosion and other structural weaknesses allowed the stringers to fail, creating a zipper effect.

The AD being released in relation to the Southwest incident would require external fuselage NDI inspections after every 500 cycles. The aircraft involved had 42,569 cycles at the time of the incident. Operators that have installed an external doubler, as long as it meets previous AD specifications wouldn't have to do the extra inspections, after the first one.

I remember the AQ243 incident when it happened. It's a miracle that the pilots were able to land the aircaft. At one point the pilots looked over their shoulder to check on the passengers, and they were looking down into the cabin, because the nose of the aircraft had flexed up so high. They had very limited communications with the tower, due to noise in the cockpit, they landed at a very high rate of speed, because they had no flaps, and they didn't dare use some of the flight control systems, due to the stress on the airframe they could cause. They wound up barging the aircraft to Honolulu, where it sat for months, before being sold for scrap.

This particular incident, being near the tail of the aircraft could have had disastrous consequences for the crew and passengers if it had failed the way AQ243 did. AQ243 did a lot to increase awareness of metal fatigue, because aircraft in Hawaii have MUCH shorter cycles than others, so they put a LOT more strain on the airframes (the longest flights are 45 minutes, the average ones are only 20). Hopefully this AD will be passed, and they will be more aware of metal fatigue as airframes age on newer airframes.

posted on Sep, 15 2009 @ 03:29 PM
reply to post by Zaphod58

Interesting. Hadn't heard about Clara Belle's body blocking the initial gap in the fuselage skin...I tend to find that a bit hard to believe, given the amount of OTHER material, such as ceiling panels, inside the cabin.

HOWEVER, what I do remember (and haven't looked into it for many years) is this:

It WAS quite old, the -200 Aloha airplane, with a LOT of cycles, and a harsh life out there in the Pacific environment (salt air).

My understanding was that both the AUTO and STBY pressurisation systems were inop, and they were dispatched in MANUAL. (The airplane had been operating that way for several days).

The CABIN over-pressure relief valve was found (after accident) to be corroded, and not functional.

It is theorized that the First Officer (later a Captain, although Aloha is now out of business...) mismanaged the pressurisation, and exceeded the maximum PSID.

Not sure if that finding still stands.

Also, it seemed, from the damage, that the initial break point was at the joint between the forward Section (forget its Boeing reference) comprising the Flight Deck, and the first fuselage cabin section assembly. Relative wind forces did the rest, once the skin ruptured, to tear off the upper portions....

posted on Sep, 16 2009 @ 01:38 PM
reply to post by weedwhacker

There was a qualified gentleman who did an independent investigation (extremely comprehensive) who found evidence of a blockage causing the stringers to not do their job properly. When he blew up the pictures of the fuselage, and examined them, he saw what appeared to be blood on the outside of the fuselage, immediately behind the aft portion of the tear. It appears in some pictures that when C.B. Lansing was pulled out, her head or some portion of her body impacted the fuselage. His theory was that there was an initial "small" hole, that pulled her into it, which then caused an overpressure situation which blew out the entire section of fuselage.

According to the accident reports that I remember, there were no system or other write-ups on the aircraft when they began flying that day. Interestingly, there was an ATC controller jumpseating with them on that particular flight. The aircraft in question at the time of the incident had 89680 cycles on it. The aircraft that had the hole in July had 42569 cycles. (Pictures of the panel removed from the Southwest flight)

[edit on 9/16/2009 by Zaphod58]

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