PPRuNe Forums - View Single Post - Paul Phelan’s article in The Australian on Fri 10 Aug.
Old 18th Aug 2007, 13:26
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Following article courtesy of The Australian:

Crashed Shrikes were overweight

Paul Phelan | August 10, 2007

GOVERNMENT officials were warned 25 years ago that Shrike Commander aircraft like the one that crashed near Melbourne on July 31 were allowed to fly at weights 10 per cent higher than they were designed for.

At least 25 Aero Commanders worldwide have disintegrated in flight, another having crashed fatally in Tasmania in February 2004 when a wing separated.

Flying at heavier weights increases the risk of structural failure, and the deadly mix of turbulence and latent fatigue can trigger in-flight break-up.
In the US, their country of origin, Shrikes are limited to a 3062kg maximum takeoff weight, but when they were imported here as used aircraft, the (then) Department of Aviation issued a "supplemental type certificate" allowing them to fly at up to 3357kg, the equivalent of three extra passengers.

Though CASA insists that test flights were carried out to prove the aircraft's capabilities, performance engineers from Gulfstream American Corporation, its manufacturer told Australian operators the assessment must be wrong.

"If we thought it would fly 10 per cent heavier, we'd have certified it at that weight, sold a lot more planes, and made a lot more money," said a Gulfstream engineer. The decision created such dismay at the Government Aircraft Factory, which was building competing aircraft, that its management hired a Shrike Commander and its chief test pilot flew a series of test flights to evaluate its engine-out performance against certification requirements.

Though aircraft in this category must show they can maintain a 1 per cent climb gradient with one engine shut down, tests showed it didn't quite meet the requirement even at the US-certified weight, and it couldn't even maintain height on one engine at the higher weights approved in Australia.

Consulting aeronautical engineer Malcolm McLeary supported calls for a review, saying there appeared to be three good reasons why it was warranted: "The manufacturer has not designed or the state authority of origin has not approved the operation to the higher all up weight figures. The higher weights were unilaterally taken by Australia only. The flight tests of an Aero Commander carried out by GAF show non-compliance to the certification standards. And the power loading for the type (weight per available horsepower) is suspiciously high when compared with other aircraft supposedly designed to meet the same requirements."

Mr McLeary said that to carry the extra weight safely, the Shrike would have needed at least 15 per cent more horsepower than it had. He also scoffed at the DoA's suggestion that the GAF test aircraft's performance was due to age: "This would indicate that the flight test aircraft had in fact degraded by over 20 per cent, which is unlikely."

The Gulfstream engineer agreed that the performance of an aircraft that had flown only a little over 3000 hours could be degraded by 20 per cent: "Well, maybe if it was run over by a bulldozer," he quipped.

CASA engineer C. S. Swift, when he published a detailed study of the Shrike's woes, exclaimed: "How was it that such fundamental structural problems were still unresolved after 40 years?"

But 12 years later, about 50 Shrike Commanders are still flying in Australia. More than half are registered to General Aviation Maintenance Pty Ltd, the operators of the crashed plane, and they are still certified to fly here at a 10 per cent heavier MTOW than the US regulator allows.

The Shrike remains popular with commercial operators because of the weight concession, but its pilots are now worried that the average aircraft in Australia has flown about 25,000 hours at unusually heavy weights.

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Without commenting on the veracity of the article it is worthy to note the article states:
GOVERNMENT officials were warned 25 years ago that Shrike Commander aircraft like the one that crashed near Melbourne on July 31 were allowed to fly at weights 10 per cent higher than they were designed for. (my bold Italics).
That statement appears to be confirmed by this CASA pdf document and does not attribute the recent Shrike accident in Victoria to the Australian DCA/CASA approved higher gross weight for the Shrike.

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