Sunday 26th

Well, got to the field around one. Rigged the Gangster just in time to pop it under Brians ground sheet as the rain came down
Thankfully it cleared up and the weather got better and better.
There were two highlights of the day for me. First my good friend Brent got his A fixed wing under the watchful eye of Rich. Thanks Rich. Brent is over the moon as the model belonged to his brother who passed on a few years ago and he realy wanted to fly it. Brents application form is in the post as we speak so you will be seeing a lot more of him in the future.
The second event was Andy maidening his jet.























Only a short flight due to pump problems but it looked, sounded and smelt great.

Nice on Andy .

I got in one flight with the Gangster before the Irvineall compression Still the Raptor flew well and the motor is getting better every time out.

DaveS

Nice one Andy, bout bloody time

About time indeed! Cheers for all the help today folks, much appreciated!

The maiden was a little hairy if I am honest! The take off was not too bad, but it seems the boomerang doesn't need much throws on the ailerons especially! Once I had got that hang of that, somebody nicked the fire out of the engine! Sooo, a deadstick landing with a jet that still has about 2 litres of fuel onboard, with no idea of how it slows up, stalls, or the behaviour with the flap out Good fun though! I see you have been kind with the pictures though Dave, none of the second and third bounce on the landing ?!!

That was it for the day though, as the fuel pump seems to be a bit iffy. It works, but won't spoll the engine up past 135krpm (it should get to 160kprm). That explained the last two aborted take offs though, the engine will have only been putting out about 4.5 kg thrust, instead of around 7kg.

Still, it was a rather good day

Roll on Next weekend now

Cheers
Andy

Oh, and Dave, send me a copy of those pictures in decent resolution would you? My email is andy(at)andy-sayle.co.uk (change the (at) for an @). email should be okay up to about 15Mb

Cheers
Andy

Congrats to both parties, sounds like a good day sorry i missed it!
Hey Andy, no bicycle clips on the shorts!!!
Glad all went well hope the pump gets sorted.
Bob G

I figured it would be best to wear baggy shorts, and let the air circulate

The pump issue is well and truly baffling me though. Out of the model it seems fine, having a good flow rate, and not binding/sticking etc. In the model, it will only provide enough fuel to the engine to get it up to 135krpm, instead of 160krpm, and that is the pump running flat out too.

Methinks a redesign and replacement is called for

Cheers
Andy

andy . when the pumps in the model does it have to pump further than when you ran it on the bench?

I thought that might be the issue, so I replicated the instal with about 1m of tygon tube on the inlet, and 1m of 3mm festo on the outlet. This makes the total pipework a bit longer than that in the model. The only difference was a lack of an air trap type header tank filter thing (I used a felt clunk as per the tank in the model too).

It's baffling me though, as I found the flow rate for the pump I have. This one seems to meet it fine on the bench. I'm going to have another shot at testing it drawing fuel from the tank in the model (through the air trap) and measuring the flow rate/current draw there to see if it gives me any more clues.

Steam is quite clearly the way forward if the pump is a bit iffy though

Cheers
Andy

Speaking with my mate Steve, he tells me that on his Jet Cat unit the max RPM is set by the ECU. Could it be that yours is limiting the max RPM Only a thought.

DaveS

Yeah, mine is set in the ECU too. I checked it at the field, and the max power rpm is set to 160krpm.

I think I have narrowed the cause down a little. I have checked the ECU logs (it records the last 50 minutes operating parameters in a log file) and the pump is running flat out when the engine is reaching 130krpm. That means there is either:

A blockage (dirt, crap in the fuel lines somewhere)
an air leak
or the pump is a bit sticky.

The investigation continues

Cheers
Andy

you out for another try tonight andy? weather looks good so think il be down there.

Hello India calling hello can you hear me
Well done to Brent on passing his A test and to Andy for flying his just I would have love to been there, but bloody work! We have not had a rest since we got here!

Internet is slooooooow


Keep up the good work guys, looking forward to hearing/ Reading the next report and all the best

India out

Zaidy

Leigh wrote:you out for another try tonight andy? weather looks good so think il be down there.

Unfortunately not, no. I have no car SWMBO is playing netball in Llandudno so I am being deposited at the top of the Great Orme, complete with Mountain bike, and being told to get home using pedal power!

I've just checked the forecast though, and it is looking good for the back end of the week/weekend

Did someone say something about Indians? I had a wicked Curry on Saturday night (where is the fire coming out of one's ass smiley when you need it?)..... When are you back in the UK Zaidy?

Andy

[quote="Andy Sayle"]About time indeed! Cheers for all the help today folks, much appreciated!

The maiden was a little hairy if I am honest! The take off was not too bad, but it seems the boomerang doesn't need much throws on the ailerons especially! Once I had got that hang of that, somebody nicked the fire out of the engine!

Hi Andy
Ooooo I wish I had one !!!!! and I knew more about jets

Hey andy

Should be back home by mid to late June. But it's not soon enough!
This job has been none stop I need to get back home and get some flying done!
Regards to all..
Zaidy

PDQ wrote:
Hi Andy
Ooooo I wish I had one !!!!! and I knew more about jets
I note your logs show that you aren't achieving max limit revs once in flight.
Just a thought, maybe the engine's fuel feed rate needs to increase once it's in flight.
The fuel pump is doing well enough on the ground, but maybe, not good enough in flight. Or the throttle mixture setting needs tweaking ( if this is possible) to strike a compromise between on ground and in flight.
Simply, the in flight power/load/speed are quite different from on the ground.

You are welcome to have a demo of my engine down at the field any time over the summer (well, anytime I'm not working!). I'm hoping to get a buddy box system sorted out for my TX, so that I can let other people have a fly of it too. I might as well spread the enjoyment out a bit

Just a bit of background regarding turbine operation (on any scale!), is that their speed and power output is governed solely by the amount of fuel put in. The more fuel is pumped in, the faster the turbine operates, and the more power it generates. It is very easy to overspeed a turbine simply by pumping too much fuel in!

The electric fuel pump for my engine is the throttle control for the engine. What is happening on my Boomerang, is that the fuel pump cannot deliver enough fuel for the engine to get to its maximum power rpm setting (160krpm, where the fuel pump is electroncially limited to prevent overspeed and damage). This is happening on the ground, before it even gets into the air. The fuel pump is being driven by the ECU as fast as it can by passing on the full battery voltage to the pump. It is impossible for the pump to go any faster, and this is only resulting in an rpm reading of 135k (25k down on the max power rpm, and about 40% down on power as a result).

The causes for this are pretty simple. Either there is a blockage somewhere in the fuel lines/filters, there is an air leak somewhere, or the pump is faulty. I'm still trying to figure out which it is, but I have ruled out air leaks. A blockage is unlikely (all lines have been blown through with air before putting fuel in) so it is pointing towards a faulty fuel pump. I'll get to the cause of the problem eventually though

Just in time for the summer then Zaidy

Cheers
Andy

Andy, just a thought, not that I know anything about jets, but are the battery volts getting to the pump?? ie HR wiring, sus battery pack with too low a capacity/high internal resistance (high current draw results in volt drop at full throttle), etc. Thus, full throttle (max pump o/p) is not full throttle.

Any air, the smallest of bubble that gets into the fuel line, will cause the engine to stop immediately. Unless your using a bag tank (plasma bag), you must have a header tank with an airfree valve (felt clunks don't work) and absolutely no air whatsoever in the fuel tank. BVM do the perfect fix but not cheap. To check for airleaks, just run the engine up and if you have a leak, the fuel feed line to the engine will show up immediately. Are you using the required cut off tap? Some guy's found the servo jittered with interferance and caused it to close. Suggestions to help you along the way. I'll have to get mine out of moth balls now (photo in the gallery) but come June it is unsafe to fly anywhere near the corn field till September.....

I think I have found the problem! I came to set the pump running at around 2v on the bench for an hour or two to re-bed it in again, and see if that improves things. Lo and behold, the pump has siezed again. I did run it on the bench the other night, and noticed the pump would occasionally hiccup a little bit, so I am suspecting there is a bit of debris in there from somewhere.

God knows where it has come from though, I filter the fuel before mixing it with turbine oil, I filter it again before putting in the fuelling station, and again before it is pumped to the model, and again when it leaves the main tank to the header tank, and again when it leaves the header tank to the pump!

Having tested all the onboard piping, filters and whatnot, I'm pretty confident this is the root cause of all the issues I had on Sunday, so a replacement pump should be on its way any moment now

Cheers
Andy

If you need a hand with the "tie wraps" then I'm more than happy to help.

I hope it resolves the problem, nothing worse than "bad preparation"

Ha, bad preparation It worked great the last time I ran the engine up!

I meant to add a PS to my previous message too. Why is it unsafe to fly anywhere near the corn field after June? Does that apply to Petrol powered models too? How about Lipo powered models?

All of them have some pretty volatile things on board. Lipos can catch fire easily if shorted out, ESCs can catch fire too (easily possible in a crash). As for petrol, then all that takes is the slightest spark to ignite it.

Just wondering

Cheers
Andy

I can honestly say I've not heard that one before, it's going to be pretty difficult not to overfly the corn for landing approach with the westerly winds.

Andy Sayle wrote:Ha, bad preparation It worked great the last time I ran the engine up!

I meant to add a PS to my previous message too. Why is it unsafe to fly anywhere near the corn field after June? Does that apply to Petrol powered models too? How about Lipo powered models?

All of them have some pretty volatile things on board. Lipos can catch fire easily if shorted out, ESCs can catch fire too (easily possible in a crash). As for petrol, then all that takes is the slightest spark to ignite it.

Just wondering

Cheers
Andy

Your right about petrol and lipo's but then I didn't want to bring that up, should a plane catch fire in the corn field, well you won't get round to it to put the field out let alone the aircraft. The turbine on the other hand is another matter .... a flame is coming out the back and shoots hot gases a long way, as well as extremely hot even after shutdown, hence the reason why I don't fly my turbine when the corn is ripe to catch fire or suck the debris in and trash the engine.

that corns been ripe a loooong time cmon get it flown