Light aircraft down north of Bathurst

[alidad]

The RAAF had a wing fail on a Macchi the late 90's. Unfortunately the bangseat was of little use then (RIP). A big budget does not necessarily protect you from such an unfortunate event.
The earlier model seats were/are not zero/zero designed ( Z feet, Z speed), nor do they have the stability systems etc incorporated in modern designs. If you end up in a dynamic UA at low level with a major structural failure- your time is up.

The following is a technical overview of the fatigue issues involved.

http://www.dsto.defence.gov.au/publi...TO-TR-1657.pdf

[Milt]

Evidently the Strikemaster suffered a right wing seperation. The usual event when a wing failure occurs under high load is for the two wings to clap together. This negates the potential for crew survival using ejection seats during the following break up. I know - I've been a smidgin away from a wing seperation when a main spar failed and I know that my ejection seat would have been unuseable.

Significant in the accident analysis will be the design g loads for the Strikemaster. I would guess max g to be 6.0 with an ultimate of 9.0. Can anyone advise the cleared max NzW?

[VH-XXX]

You don't see passengers in Cirrus aircraft pulling handle to deploy the parachute, so why would someone be stupid enough to try and eject themselves in flight...?

Has a passenger ever pulled the handle in a Cirrus??? No.

[Joker89]

Article in The Australian today

Crash jet operators urged to reassess safety
Steve Creedy, Aviation writer
10oct06

OPERATORS of Strikemaster fighters in Australia were urged today to reassess the airworthiness of their planes after air crash investigators confirmed that an aircraft that crashed near Bathurst last week came apart in mid-air.

RAF veteran and experienced adventure fighter pilot Nick Costin and a man celebrating his 50th birthday died when the jet crashed during a joy ride in the Central NSW on Thursday.

The Australian transport Safety Bureau said yesterday access to the crash site was still being hampered by a bushfire sparked by the crash.

However, investigators had been able to reach some of wreckage strewn along a trail extending more than a kilometre.

"The team located and examined the aircraft's right wing and reported that the wing had separated from the aircraft fuselage in-flight,'' the bureau said.

"At this stage, the ATSB does not know where in the wreckage trail sequence the wing is located, or the reason for the separation.''

Investigators have also been looking at the plane's operational and maintenance records and expect to release a preliminary report in 30 days.

Meanwhile, the Civil Avaition safety Authority is urging operators of the jets to make sure they have addressed British warnings about problems with Strikemasters.

Australia has issued two airworthiness directives concerning Strikemasters, including a warning about problems with wing components.

"Because of the possibility of a structrural failure we recommend that owners and operators reassess the airworthiness of their aircraft,'' said CASA spokesman Peter Gibson.

"We are pointing to them that there is a 1996 airworthiness directive which talks about the need to inspect the port and starboard main spar upper attachment lugs for cracking.''

[noooby]

Don't remember what the 'g' limits were for a good Blunty.
In my time in the RNZAF, I never saw a Blunty that wasn't 'g' limited (although I only saw them in the twilight of their career). I do remember that some had a 4g limit, but most of the ones I saw had a 2 or 2.5 g limit, and circular patches of silver tape all over the sings where the cracks were being monitored.
Blunty wings didn't like the turbulent air that prevails in NZ

[moreorless]

http://www.abc.net.au/news/newsitems...0/s1759620.htm

But CASA says at this stage there is not sufficient evidence to ground the jets.
Mr Gibson says owners must make decisions on whether to ground their planes or cease joy-flights based on the jet's maintenance history.
"If they've been making regular structural checks then these aircraft should be fine to continue flying," he said.
"For those operators who haven't been doing that recently then certainly our advice is make those checks now."
--------------

The checks should be part of the maintenance program.

There are two AD's out on the aircraft particular to the wings. These limit loading and also prohibit flight after the expiration of 2FI units after the issue of the AD's until the AD's are complied with. My understanding is load restricts are removed after the AD's are embodied.

[asac]

a disaster waiting to happen

Does anybody here really believe that CASA does anything but a superficial job in overseeing the operations of limited category aircraft. This was a disaster waiting to happen. Heads need to roll at CASA or we will loose more good men. Check out limited category operations at YWOL. It the ASTB does have a full investigation god help CASA.

GIBSON must be stupid how could he say

"If they've been making regular structural checks then these aircraft should be fine to continue flying," he said.

Limited category aircraft fly civilians no if's they must.

[Trash Hauler]

Even when a major structural failuer occurs it would be rash for the regulator to ground all of that type until they are reasonably certain it is a fleet wide issue and all aircraft are in imminent peril.

Remember the JAL 747 accident. Should B747s have been grounded world wide after that accident. Of course not. The cause needs to be identified and then the risk to each aircraft assessed. The same with the China Air B747 breakup. Out of that investigation came a series of recommendations and ADs to prevent a recurrence but no other B747 was in imminent peril (about to have the same failure days/weeks).

In my aviation career I have only experienced one fleet grounding and that was early on in the military. Ironically it was not required as the cause of the accident was identified as a known flight characteristic combined with mis-handling by the pilot.

TH

[VH-XXX]

Said Chieftain is the one that broke apart when it flew through a thunderstorm on the way to Vic last year.

[Trash Hauler]

I can understand why none of the Chieftens were grounded. Severe turbulence from thunderstorm activity is likely to have precipitated the breakup.

http://www.atsb.gov.au/publications/...200506266.aspx

[Evil Ultralights]

Right you are

The cause needs to be identified and then the risk to each aircraft assessed.

This is exactly right and why CASA have not grounded the remaining Strikemasters owned by other operators in the country. Fact is the AWB which was issued on the 10th Oct is nothing new. This has been around since the mid 90's. Required wing mods were done on many of the Strikemasters whilst still in the employ of RNZAF for example. Apart from that operators are already required to conduct regular inspections of the wing spars, which is being done and has been done to date by at least 2 of the operators in the country. The plane that crashed by NOT RNZAF as the others are but was ex Singapore Airforce. The pilot flying held a commercial licence for a relatively short period and was not, as is widely reported, an ex RAF or ex RAAF pilot.

Also keep in mind the mods were primarily ordered because of the way the RNZAF and other such Air Forces were flying the aircraft, full of ordinance and in situations with high g loading.

So with the mods and regular NDT inspections which will pick up any fatigue cracks there is no reason to ground perfectly good aircraft.

In the hands of the right people with proper care and maintenance they should be no problem and in fact the other 2 operators of these aircraft have NEVER had ANY maintenance issues of any sort with the planes. Now there is not many aircraft that that can be said about.

Maybe the pilot induced too much rolling G , perhaps it was to avoid something, perhaps a bird. Who knows? These planes do not just "fall apart".

Evil

[Chimbu chuckles]

Would not under wing ordinance/stores tend to help with + G tolerance (wing root bending moments...a bit like zero fuel weight?) If that is the case perhaps lots of pulling in civvy street without under wing stores might aggravate to the fatigue problem rather than mitigate it.

Just wondering.

Rolling G may very well end up being a suspect...am I right in assuming only one wing came off?

I have seen a sort film of a PN68 used for a 'Hoover style' aerobatic display shed both wings simultaneously outboard of the engines as the pilot pulled into a loop

[404 Titan]

Chimbu chuckles

Reading "Evil Ultralights" post I was thinking the same thing. Wing ordinance should reduce wing bending moments caused by high “G’s” just as a cargo/baggage load in the wing lockers on some light twins doesn’t need to be included in the limiting ZFW calculations.

As a side note I remember seeing that video of the PN68 with folded wings many years ago. What made me cringe was that the pilot’s wife was doing the PA commentary at the air show at the time.

[Milt]

404 Titan

The extra weight of under wing stores under applied g will only alter the the wing bending moments locally along the wing. The bending moment at the wing roots will be unchanged as the wings still have to support the fuselage to the same extent at any increased manoeuvre loading. This can become complicted if there is a factor of fuselage lift.

The hazardous effects of rolling g are generally underestimated by most pilots and should receive more emphasis in training.

[moreorless]

Originally Posted by Milt

404 Titan
The hazardous effects of rolling g are generally underestimated by most pilots and should receive more emphasis in training.

This is a very good point. Cockpit G-meters are centreline in the aircraft and only represent the G-loading at that point and do not indicate wing loading when the aircraft is rolling.

[Arm out the window]

You'd hope that the pilots of these kinds of machines would be well aware of the rolling g limits which would be published in the flight manual.

[moreorless]

Originally Posted by Arm out the window

You'd hope that the pilots of these kinds of machines would be well aware of the rolling g limits which would be published in the flight manual.

I would hope that pilots of any machine know (sadly most don't) the G limits and know how those G's are determined and how they apply. We all learnt about 2G level turns - 2G's - but of that - where is the 2G and what kind of load is applied on the high wing when - as is typical - the nose is too low and is pulled up with elevator in that "2G" manoeurve to achieve a nil vertical speed rather than some spiral dive look alike.

Don't kid yourself - all pilots of all machines should be aware. All aircraft can easily exceed the structural limits of the aircraft and rolling G is little understood.

[Brian Abraham]

NATOPS manual on the aircraft we flew limited rolling G to two thirds of the symmetrical flight manual limit. Under wing stores did not affect G limits. If flying in moderate turbulence G limit was reduced to two thirds of flight manual limit to allow for turbulence induced additional G. Flight manual limit 6G hence two thirds was 4G. Naturally this may not apply to Strikemaster.

[Runaway Gun]

Underwing stores definitely do reduce the G limits in most aircraft types.

[Milt]

Runaway Gun
In the context of the present discourse we need to understand/comprehend why g limits may be reduced with underwing stores/integral fuel tanks contents and the like.

The current designers will have complex computer programs to provide the answers but we users need a simplistic comprehension as to what goes on when we load up our wings in flight particularly in the case of asymmetric wing loading.