Tag Archives: engine mount

Plane sailing

The fatigue testing has been running really well, practice makes perfect as they say! We’ve been busy changing all the joints of the Whiffletree and replacing the engine mount bolts. This is done at approximately 60,000 cycles. We learnt some lessons during the first period when we had rig failures and bits breaking, but this means the second time round, we can monitor things better and avoid this from happening again. In addition, we made a plan with Game Composites to change certain rig components as a matter of course.

We’re currently at 61,500 cycles and we have to get to 71,663. When we run a 24-hour period it gives us 8,640 cycles, so in running another 24-hour period we will be left with only 900 cycles remaining before we reach the finish line and the golden number of 71,633.

Once we’ve reached the 71,633 cycles, this will also us to begin boxing up the airframe in insulation and the week commencing the 21st we will be doing another ultimate load test at 72 degrees Celsius and then a further ultimate load test at a 15% higher load. It will be getting hot in Catcliffe! So keep checking back for exciting news!

Stanley knives and Saturday Morning Kitchen

We starting running the second life of the fatigue testing cycles on Friday and to our delight it ran beautifully well, so ran through Friday night as well. Set designer Steve gave up time on his Saturday morning off to come and shut down the rig safely for the rest of the weekend. Always absolute dedication from us here in ASTC could cause us to miss Saturday Kitchen Live.

We came back in on Monday and started our usual rounds of inspection to find that the engine attachment bracket (the bracket that takes the main load up into the wing spars) was starting to show signs of cracking.

The solution was to take it off, do some hasty cutting up of bits of box section we had and got the whole thing welded up much stronger with the help of our friends at Nuclear AMRC. This time we’ve really gone to town and beefed the bracket it up to help ensure it won’t happen again.

It was ready to reinstall this morning and we are ready to continue with the fatigue testing again today. We have already clocked up about 20,000 fatigue testing cycles out of the 71,633 required for the entirety of the second life testing, so we are getting through it quite quickly now.

Luckily for ourselves and Game Composites, nothing untoward has happened so far during testing with the extra damage we have caused the airframe. Game Composites came in late last week and did some repairs to the rear stabiliser of the aerobatic aircraft because we had noticed a little crease was developing.

It’s quite remarkable the aircraft can be repaired. A Stanley knife is used to cut out the damaged patch of composite material on the fuselage to reveal the foam layer in the middle. The foam is removed and smeared with glue, but not just any old glue is used; the glue has what only can be described as lots of hollow tiny glass balls in it, making it lightweight yet very strong. This replaces the foam and a patch is stuck over the top with resin which we leave to cure overnight.

As the aircraft being hand laid-up (or built by hand), it’s relatively easy and cheap to repair, as any repairs can also be done by manually without having to send it back to a manufacturer. As it would at the hanger or in the field.

With the repairs to the engine bracket made, we will be back up and running with testing today and we will hopefully conclude the second life fatigue testing next week so we can get ready for further testing. Exciting things to come for us!

Sometimes good things fall apart, giving us a chance to build better for the future…

After having a great week last week running the Whiffletree through the night and flying through some more of the fatigue testing cycles, we unexpectedly encountered a failure of the bolts connected to the engine mounting bracket.

That area of the aircraft is more highly loaded during testing than it would be in real life when in-flight, so it is running through the fatigue cycles in an ‘over-test’ situation. Unfortunately the bolts, which are grade 12.9 high tensile bolts, simply weren’t strong enough and had fatigued over time.

The failure caused the bolts to shear and pop off the rig, allowing the engine mounting bracket frame to bend, ripping through the weld and bening the arm of the bracket out of line.

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The sheared bolts from the engine mount bracket

 

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The failure ripped through the weld on the bracket

 

All testing stopped without any damage to the aircraft and we had to remove the whole front engine mount bracket to grind the entire weld out. This took Mission Controller Shane an entire day before we could then pull the bracket back into place and tack weld it together ready for re-welding.

The bracket was sent to our Nuclear AMRC colleagues who welded it back together on Monday. When it was returned we had some re-fitting to do, as the re-welding was done to both sides of the bracket instead of one this time. This caused the bracket to close up slightly from its usual shape so we had to jack it out to make sure it would fit.

The extra strength should serve us well as the fatigue testing continues, so taking the bracket off turned out to be a good opportunity to make some improvements and plan for future preventative maintenance; such as changing the bolts on a more regular basis.

The rig was back up and running this morning, so we conducted a 30 minute test run to bed the rig back in. We will then go round the rig, tighten everything back up and make sure nothing has moved out of place before resuming full testing again this afternoon and evening.

So even though we are only up to 54,400 fatigue testing cycles, should today go as planned, we could be back on 24 hour testing as early as Wednesday; maybe even finishing the fatigue testing completely by Friday!

Pop back next week to see what happens!

 

The Big Flip

shutterstock_123022126One of the more immediate challenges we will face with the plane is flipping it so that we can mount it on the whiffletree – it will sit on the rig upside down. There was some talk of using man power to flip it but Shane’s got another plan!

Here’s how we hope it’ll work….

The bearing that’s fitted to the engine mount, that’s mounted to nose of the plane, has had a hole drilled in it so we can fit a rotating turn buckle inside. The rotating turn buckle will be lifted using the crane.

At the back end of the plane we’re going to make and mount a bracket that’s got a centre hole in it, again with a turn buckle inside. We’ll need to arrange some more lifting equipment to then lift the plane from the back end too.

The plan is then to lift the plane up at either end to a height of about 4 metres – remember the wings will also be mounted by this time too. Someone will hold one wing so as we’re lifting the plane up they’ll walk the wing through and ultimately flip the plane. The first ever barrel roll inside the ASTC!

We’ll keep you updated on how this pans out! We’re hoping the big flip will happen in early September.