Tag Archives: testing loads

Gearing up for a big day…

As Mission Controller Shane was away last week and the AMRC was very busy with the exciting budget day reporting hosted by Sky News here at the Advanced Manufacturing Research Centre, the team decided to spend last week re-boxing up the aircraft with insulation and heaters ready for a set of ultimate load testing this week.

The second life fatigue testing was completed successfully the week before and now that the Mission Controller Shane is back, he is currently validating the testing programmes for this week’s testing.

This week’s ultimate load tests will consist of a residual strength test where the Game Bird 1 is pushed up and pulled down on the Whiffletree rig to 72 degrees, applied by a load of 64.5 kilo newtons; the same forces applied throughout the fatigue testing.

Once complete a heated static ultimate load test will pulling down the plane on the rig first with a force of 82.65 kilo newtons, then the aircraft is pushed up on the rig plus 15 per cent of that force.

As we are still experiencing some play in one of the wing pins, Game Composites are currently assessing whether they want to complete some repairs to the damaged bushes this has caused before we go ahead with the testing tomorrow, so Game could well be back on-site with us this afternoon.

As well as Game, the Civil Aviation Authority (CAA) will also be present on-site to witness the tests and we will update as soon as possible, hopefully with some video of the nerve-wracking testing, so you can experience what the team go through when putting the Game Bird 1 through its paces!

IMG_0505
The Game Bird 1 boxed up and ready to go!

 

Passed with flying colours!

Today was a great day! Last Friday, after all the ups and downs, we finished all the fatigue testing after we reached 71 633 cycles.

With this complete it was time for us to move onto the ultimate load test, performed once before, where the aircraft gets boxed in insulation and heated up to a toasty 72 degrees Celsius. This definitely helps take the edge of the February chills we have here in South Yorkshire.

So with the airframe all boxed up as you can see in the picture, we were all ready for the residual strength test to 64.85 kN which the airframe had no trouble getting through.

When this first pre-load test was complete, we moved onto the static ultimate load test which took the Game Bird 1 up to 82.65 kN. This is the highest loading that the airframe has seen to date, so it was a tense time for all involved. The Game Composites team were on site during the testing today, so we were all feeling the pressure!

17.02
The Game Bird 1, boxed in insulation for today’s ultimate load testing.

 

Fortunately relief spread across us all when the airframe passed with flying colours. There was the odd creak which was expected, although this didn’t help with the tension levels when we were all watching!

It has certainly been a very exciting week for us here at the AMRC and guided by the Civil Aviation Authority (CAA), it is now time for us and the team from Game Composites to decide what’s next when it comes to further testing for the Game Bird 1 aerobatic aircraft!

Stay tuned!

Even the best laid plans…

We’ve had a fairly good week at the Advanced Structural Testing Centre since our last post. As mentioned the customer visited us to see the aerobatic aircraft in action on the whiffletree testing rig to check out an unusual creaking sound and to review the data sets captured every 10 cycles of fatigue.

The aircraft is assembled on the whiffletree in an asymmetric way to induce twisting into the wings and fuselage as the load is applied. To achieve these torsional loads, it is necessary to mount the whiffletree on the right wing in front of the centre of pressure (CoP), to induce the correct amount of ‘twist’ in the left wing that is mounted slightly behind the CoP. Loading in front of the CoP wouldn’t happen in normal flight.

This means the right wing is not being tested representatively (it is being over tested). As the root spar of the left wing is smaller, which is the critical wing for testing; so if the left wing is good and the identical right wing with a bigger interface will also be good.

As the right wing is carrying this forward CoP twist it was necessary to put some patches on to stop the flexing of the skin inside and stiffen the assembly, hopefully preventing the unusual sounds, data and make the test run smoother.

The fatigue testing continued on Friday and Saturday morning and on Monday we felt confident enough to let the testing run through the night.

We set the testing cycle going at 4.00 pm and as all good parents do – kept a keen eye on its progress via a webcam – we do like to know what our children are up to! Just after 10pm the shutdown lights came on as the rig was no longer running. A brief investigation on Tuesday morning found the reason for this was a fatigue failure of a rig part.

The part was the thread of an adaptor where the actuator is joined to the load cell; this had fatigued and broken so the actuator could no longer put the loads onto the rig.

img_0344crop[1]

The MOOG controller had then automatically shut down safely. As the actuator became detached it fell onto the engine fairing attachment beam below the representative engine mount causing some damage DOH! This is the worst nightmare of the test engineer! Fatigue testing really does discover every little issue with the entire system.

img_5131crop[1]

The damage has not caused any structural problem to the aircraft and the customer was more pleased that we had tried to run through the night to get the test completed more quickly. Repairs were made by the customer on the same day.

We are now modifying the back end of the load cell to change the broken part to a larger diameter, this is so it will connect directly onto the actuator, hopefully minimising the risk of this failure reoccurring.

The larger diameter part is currently being machined by our AMRC apprentices based onsite at the Knowledge Transfer Centre workshop. A great advantage of being so close to our other centres here at the AMRC is the ability to collaborate closely with our colleagues and our customers, allowing us the flexibility to modify and repair parts at short notice. The apprentices are machining the modified part which should be back with us by the end of Tuesday, allowing us to start testing again on Wednesday if possible.

We are now just under 30 per cent of the way through the testing cycle, so once the modified part is fitted and we are running the fatigue testing cycles day and night, we should run through them fairly quickly!

 

Passing the ultimate load test…

This week the team have completed the ultimate load test on our aerobatic aircraft under heated conditions. The test involved applying 82 Kilo newton’s (kN) of force through the load mounting bracket that acts through the main wing attachment points. The load is spread through the airframe and reacted down through the Whiffletree all under heated conditions of 72 degrees Celsius!

The ultimate load test involved loading the airplane up to replicate positive and negative g forces of 15 g. This load was applied just once in each direction and is the biggest load test the plane will complete.

It is a pivotal point in the testing programme, and takes the airframe to 150 per cent of maximum operating load so it was ‘squeaky bum’ time for the aircraft designers and a real relief that the test was passed successfully.

 

So we now have a green light to go ahead and start full fatigue testing as soon as we have made some modifications to the Whiffletree requested by the customer. We’ve installed some steel metal reinforcements to the engine mount block to ensure that the load is spread evenly through the engine mounting interface on the aircraft.

The reinforcements were laser cut by our friends at the AMRC Design Prototyping & Testing Centre and welded by our Nuclear AMRC colleagues. So we’re in good shape to start the fatigue testing cycles in earnest, getting as many cycles as possible completed before site shut down for two weeks over the Christmas break.

The full fatigue testing programme is made up of 71,633 ten second cycles of +/-10 g. This will take five weeks if we run the programme eight hours a day. These testing cycles have to be constantly monitored to ensure we are hitting the loads, that the data being received from the strain gauges is correct and to visually inspect the aircraft as testing progresses to make sure no cracks appear in the structure.

Luckily the team will be sustained by a multitude of festive snacks that have been appearing in the office this week, including mince pies and Quality Street chocolates. Although half a tub of Quality Street chocolates disappeared this morning and the finger of suspicion has been pointed at the mission’s best boy, Ed. Whether the accusations are true or not will require more verification, stay tuned.

It’s getting hot in here

This week we have been making preparations for the temperature controlled static limit load test. This will involve us heating plane up to 72°cand performing a single cycle test on the structure. The plane will get pushed up and pulled down once so there’s a lot of work is going into 20 seconds worth of testing but it’s all worth it!

Show Boss Phil has been in touch with a company called SIG Technical Insulation. They kindly agreed to supply us with all the insulation material we require to insulate the plane, free of charge (he must have been fluttering his big eyelashes!). SIG pulled out all the stops to get the insulation material to us in break-neck speed. They bypassed the depot and got it delivered direct to us straight from the manufacturer in South Wales – we could get
used to this special treatment! A huge thanks goes out to SIG Technical Insulation for their support.

The team has been busIMG_1706y constructing a steel frame to lift the insulation that will surround the plane, a metre off the floor so we don’t unnecessarily heat up a lot of dead space. If we built a big box around the plane and the whiffletree as well, we would probably end up heating up around three times more the volume of air than necessary. By building a sealed chamber around just the plane, it will take less time to heat up and also use less energy in doing so, so it’s a win-win for structural testing and the environment! We are also making sure the whiffletree structure, that’s made of steel, the hydraulic actuator and the load cell are insulated too to  reduce the amount of heat they absorb and ensure there’s no adverse effects on the measurements when we do the test.

On top of the steel frame we’ve built we’ve started to build a flat table-top structure which is a bigger footprint than the plane, to allow us to sit the four big electric heaters, which will be used to heat up the insulated enclosure, on. The client fitted a thermocouple on the wing spar of the plane; the wing spar is one of the main structural points of the plane; and it’ll be that thermocouple we monitor to decide when it’s hot enough to do the test.

If everything goes to plan with the temperature controlled static limit load test,, (the plane’s design engineer is as nervous as an expectant parent so for the sake of his sanity, we hope it does!) we can move onto the next step of the plan which is to remove the insulation and perform an inspection before conduct another static limit load at room temperature. If all that runs smoothly, we will rebuild the insulation chamber around the plane and conduct a static ultimate load testat 72°c.. This means putting an even higher load onto the plane at a high temperature so it will be a tense but exciting time for us all!

If all the static load tests go to plan, we’ll have the green light to start on the fatigue test which is made up of 71,633 cycles – but more on that in the coming weeks.

Alone we can do so little; together we can do so much

IMG_1179We’re moving on nicely with the whiffletree build. Hopefully we’ll be getting the plane this week so it’s all hands on deck.

We’ve been building the load application frame. It’s all tacked up ready for the plane arriving – once we’ve mounted the plane onto it to ensure it fits we’ll then get it fully welded together. The load application frame doesn’t move (or so we hope!), it’s where the load is put onto the plane to move it.

All the bearings have also been delivered – the bearings will support everything and allow us to get the plane into the exact position we want.

IMG_1126Steve P has also been securing the interface plates to the strong floor. We’re using interface plates because; although our strong floor has specific coordinate holes pre-drilled; the rigs’ mounts don’t necessarily match where the holes on our strong floor are pre-drilled. Therefore we’ve had the interface plates made – we’ll attach these to the strong floor and then attach the rig to these. Basically it’s an adaption technique that prevents us having to drill further holes in the strong floor which could potentially weaken and damage the floor.

It really is a team effort to get everything ready but we’re soldiering on and keeping spirits high with lots of cake (what else?!).

Image Captions

Top right: The load application frame.

Bottom right: The interface plates.