Bulldog XX672

I think I heard that time expired Robinson R22’s can go back to the factory for a re-build to zero hour the paper work or otherwise are on paper scrap.

There is a huge difference between a helicopter and an airplane.
On helicopters most of the moving (and expensive) parts are always replaced (or overhauled) at set time limits during inspections.
The basic airframe does not have an hour limit because all the bits vital to flight (engine, transmission, bearings, rotor head, blades, etc, etc.) have already been replaced at their designated life limit.

BTW: The going price for a good flying Bulldog over here is $60-80,000 (30-40,000 pounds).

BTW II: Re: Cessnas…you see some in Trade-A-Plane with 10,000 hours…or more. Usually former pipeline patrol aircraft and the like. I know of one guy with about that many hours on his P210.

BULLDOG AIRFRAME LIFE LIMITATIONS

We seem to be getting all screwed up here, so better set the record straight.

Like it or lump it, full-scale fatigue testing of the Bulldog for the RAF caused a reinforcing strap on the main spar at the outer/inner wing to snap. BAe at Prestwick schemed a fix, embodied it on the fatigue test specimen and continued to test it to clear the expected (RAF) service life of the aircraft. Analysis of the fatigue data resulted in a life of 5000 flying hours being allocated before this modification should be carried out. The modification is called BH193 and it requires replacement of the reinforcing straps with items which are longer and made from an improved material. The many attaching bolts are replaced with oversize items, allowing the bolt holes to be reamed and examined by eddy-current NDT for latent cracking. When this modification has been embodied the airframe is good to a total of approx 8760 flying hours. There is another life limit on the tailplane attachment fittings, but that does not cut in until 15,000 hours.

For ex-RAF Bulldog T Mk 1s, known as the Series 120, Model 121 in civil parlance, the score is different. These aircraft operated with a Fatigue Meter and they were lifed on the basis of Fatigue Index (or FI). The CAA has allowed the aircraft to continue to operate on the basis of FI in civil life, I think the first certificated aircraft to do so. The limit of 114 FI was calculated as meaning the same amount of damage as 5000 flying hours in an unmetered aircraft. If you use a fatigue meter it counts the number of times certain ‘g’ steps are exceeded and FI is accrued only at the rate you thrash the aircraft. Handle it like eggs and you can fly for thousands of hours before reaching 114 FI. Hurl it round every corner at more tha 3g and you will probably hit 114 FI at about 5000 hours. Many of the ex-RAF aircraft are in the region of 8000 flying hours and still have plenty of life left before the modification needs to be done. These aircraft are required to have their FI calculated every year (it is done by DH Support), and as they get very close to 114 FI it has to be done every 25 hours. There is one aircraft still flying at 113.5 FI, and I am told that it will give its owner many more years of happy flying because he does not thrash it death with endless aerobatics.

As for the modification itself, at the time the Bulldogs were sold BAe estimated that the cost of parts was £10,000 per aircraft and it would take 500 manhours to embody. I suspect that these days the cost of the parts could be reduced somewhat, especially if a group of owners could come together to make the production run economical. Similarly, a single ‘production line’ for the batch of aircraft would allow the learning curve on the first couple of aircraft to be offset against the later aircraft in the production run. So, the mod is difficult and expensive, but it certainly will not cost more than the aircraft is worth, especially if you can pick up a life expired aircraft at the right price. The £13,001 paid for the one at Witham was too high for a Brit who knew anything about the aircraft. It was probably bought by an American where they fly Bulldogs on the Experimental category and just wait for the first set of wings to fall off. In contrast, here in the Uk the aircraft is Type Certificated and they all operate on a CofA – except one, I recall, G-ASAL at Prestwick, which is on a PFA Permit (and the Bullfinch of course, also on a PFA Permit).

So, a Bulldog WILL break at some stage, with 5000 hours/114 FI providing a safe limit before embodiment of a UK-designed and CAA-approved modification. Full details are available in Bulldog service bulletins and a Service Letter or contact the guys at DH Support who now look after it. From what I have been told, not enough aircraft have yet hit the buffers to make it economical to set up a small run of modifications. Perhaps in the next few years the situation will change.

I am not aware of any limitations on the likes of Cessna 152/172. Certainly the Tomahawk does. Regards the Bulldog -it can have the centre section spar done – however the cost exceeds the aircraft’s value.

Seems a shame to life these and not a dodgy flying club C152.

American Spam Cans do have life limitations based on hours. The Piper Terrorhawk for instance has lifed main spars which until fairly recently required the airframe to be scrapped.

There is now a re-life kit available from the US which has now been granted CAA approval.

Does anyone know if a time expired Bulldog airframe (being a fatigue life design certification) could have the expired components replaced and the airframe zero houred if the original design authority backed it? This is obviously a paper work problem as opposed to an engineering problem. Seems a shame to life these and not a dodgy flying club C152.

I think I heard that time expired Robinson R22’s can go back to the factory for a re-build to zero hour the paper work or otherwise are on paper scrap.

I would imagine that the ‘life expired’ components referred to for a complete airframe would be the main spar. If a complete restoration was carred out, i.e. what Steve Vizard does on the Isle of Wight for spitfires, then yes, a zero houred airframe would be the result. Certainly worth it for a £2 million spitfire, but not for a bulldog….

The RAF life just about everything, especially airframes, so this is just a case of the MOD to civillian conversion process. in this case, the aircraft would have to be reduced to components, the primary structure would have an NDT process carried out to ensure there was no degredation, components overhauled, and finally civillianisation for a permit to fly. Bit of a carry on for a light aircraft….

However, I stand to be corrected!:D

Does anyone know if a time expired Bulldog airframe (being a fatigue life design certification) could have the expired components replaced and the airframe zero houred if the original design authority backed it? This is obviously a paper work problem as opposed to an engineering problem. Seems a shame to life these and not a dodgy flying club C152.

I think I heard that time expired Robinson R22’s can go back to the factory for a re-build to zero hour the paper work or otherwise are on paper scrap.

Discovered that this item was sold for £13,001 for those who are interested in the financial conclusion of this sale.:)

She came out of a technical college in South Wales. She is fatigue life expired and the engine is high time so the guide price is optomistic.

This item was posted before the sale ended but was removed by ‘them’ for advertising. Couldn’t see the difference between this item and the Comet fuselage recently from the same sellers!:confused:

She came out of a technical college in South Wales. She is fatigue life expired and the engine is high time so the guide price is optomistic.