CAA Certification on the UFO Gyro

[Magnifan]

It is a bit complicated, there is no direct way of getting to thrust from power unless you know the airspeed as far as I can see. Power equals thrust multiplied by airspeed. Obviously to know the airspeed you need a lot more information about the configuration than torque and/or shaft horsepower.

By the way, cherry red is about 850C so your EGT guage seems about right. With the ignition point of petrol at around 270C I am not surprised at the number of post crash fires that we see normally associated with behind the power curve incidents, which have the engine at full power on impact. The chances of fire in the case of an engine out situation are far less likely in my opinion, as the exhaust temp. will drop quite quickly.

You still haven't explained the rather high EGT, is it just a matter of the amount of boost to the engine?

Enough thread hijacking for now.

[OzGyro]

Hi All

Magnifan - Thanks for the info

Pierre - FYI - Optimum exhaust temeperatures should normally fall between 500 - 700C, and as stated here the temperatue required to achieve a cherry red status is greater than 800C. If I was you I would more concerned in finding out the reason as to why your EGT'S are so high

If it were my engine I would be focussing on finding the cause and not just treating the symptoms.

Cheers
Darren

[mak]

Here is a "simple" thrust / hp calc that someone posted a while back on avcom and as Magnifan said, it is a bit complicated.

thrust.xls

(33 KiB) Downloaded 183 times

[MPL Pilot]

The temps on normaly aspirated engines are cooler. The EGT is within spec on the UFO.

Here is some EGT info from the rusubaru.com.

When do EGTs become “too high”?

This is a highly debated topic and much was written on it by various sources. EGTs are too high when they begin to pose danger to engine and turbo components. Generally, 1600 degrees Fahrenheit (871 degrees Celsius) is considered to be a good number, borderline high EGTs. It is probably safe to briefly run up to 1650F (899C) degrees. Of course you find people running and various tuners recommending to run 1700F (926C), 1800F (982C) and up to 1900F (1037C) degrees. These temperatures ARE causing damage to turbos and engine components.

So, why 1600F (871C) degrees is a good number? Lets look at the melting point of aluminum first – it is only 1220.666F (660.37C) degrees. Your engine has cast iron cylinder liners to help prevent the heat of combustion from melting the engine and the pistons are made out of aluminum alloy, which can withstand temperatures higher than 1220F (660C). But what about your turbo turbine wheel? Turbo exhaust housing is normally cast iron, so it can take a lot of heat, but the turbine wheel is aluminum. Regular turbos can sustain brief inlet temperature spikes of up to about 1600F (871C) degrees. Optimal exhaust gas inlet temperature, however, is about 1200F (660C) for turbos and their components.

On Subaru WRX and STI the length of the equal-length header runners allows for only about 300F (149C) degrees drop in EGT before exhaust gas reaches the turbo. The EGT drop is less in unequal length header runners.

So if you are running 1600F (871C) EGT, then the temperature of exhaust gas entering your turbo is about 1300F (704C) degrees – as you can see this temperature is at the limit of what your turbo can safely take. That’s one good reason to keep your EGTs to 1600F (871C). Keeping in mind that key internal engine components on a road engine are not designed to operate at excessive temperatures (above 1600F (871C)), the failure becomes certain if excessive heat conditions continue for any significant period of time.

[OzGyro]

Hi Pierre

Thanks for a very interesting and informative article, however it dosn't address the issue as to what is causing the exhaust to overheat.
How about I get the ball rolling, some things that may need to be considered.

1 - Air/Fuel ratios
2- Turbo boost pressures
3 - Injector size
4 - Compression ratios
5 - Ignition timing

Im just worried if you dont address the cause and just treat the symptoms. It wont be a matter of IF your motor fails, it will be just a matter of WHEN.

Cheers
Darren

[MPL Pilot]

Darren, I appreciate your concern.

I will double check the air fuel ratio, boost is only 1.4, injector size is standard for the EJ20,
compression ratio 8 to 1 and timing will be double checked as well.

This temp on the EGT is not abnormal. Johan has all the contacts and info at his fingertips, with 13 hours of flight,
(not to mention static runs which exceed 13 hours)
I am convinced we would have had engine failure if this engine was operating outside it's limits.

Something you should know, we had excesive vibration initially with the first exhaust, which played
a good part in it's failure. The wall thickness of this exhaust tube was 1.2mm, the combination
did not work at all.
The second exhaust, I had it made up from 1.6mm mild steel tube with a socket for movement on one section to
prevent vibration being forced through the whole structure. This exhaust lasted well, we had a problem with heat being
radiated from the exhaust under the cowling, causing damage to cables, waterpipes and engin mountings. At that point we insulated the exhaust
with a double layer of ceramic cloth. The mild steel failed due to the heat being trapped in.

This last exhaust will prove if we are moving in the right direction, 1.6mm stainless, ceramic coated with heat deflectors
to keep the heat of the cables and engine mountings ect. Ceramic protect the exhaust tube from the heat and the exhaust gas does not contaminate the
material the exhaust is made from.
I do admit, this has been a road of development, I am not aware of this type of engine
in any other gyro. I did not expect it to be an easy ride. But when we are done, it should be exhilarating
to fly this monster.


When I was busy with national service I use to drive an old Bedford (petrol) truck when we went on military missions, that old Bedford had an exhaust that was always glowing red. With today technology, a red exhaust should not be of great concern if all the rest has been done.

Cheers

[OzGyro]

Hi Pierre

Sounds like you have all your bases covered, however here is my offer to you. Get Johan to take an oil sample from that engine, I will supply the sample bottles and do the testing and diagnostics free of charge. Only after we have built up a good history on this engine will I be totally comfortable with what is really happening. I have spent 24 years in the industrial, mining and automotive industry's the last four of which have been in the preventative maintenance and condition monitoring (Tribology) including failure analysis.
I am a firm believer in the saying, prevention is better than cure.
The choice is yours

Cheers
Darren

[saraf]

HI Mpl

Great to see you guy's are coming along nicely. Your UFO looks nice.

One question? I see that you guy's are changing form Mild steel to Stainless......is stainless not more brittle than mild steel thus it will crack easier. We tried stainless and went back to mild.

REgards
Eben Jnr

[Magnifan]

Hi Mak, thanks for the interesting spreadsheet.

[MPL Pilot]

Mak, that is a piece of study material on that spread sheet. I will spend some time over the weekend
and see if I can make some sence of it.

Great to see you guy's are coming along nicely

Are you talking about Darren and myself or the UFO
Johan is very busy at the moment, he will fly the UFO on Saturday again as a diversion from work.
Regarding the stainless exhaust, de Graaf (main branch Pretoria) manufacture lots of exhaust systems
for a variety of aircraft, using stainless only. As I said, we have to find something that is reliable.
The mild steel failed after wrapping it with ceramic because of the pressure in the pipe and the heat accompaning it. Hiedie turbo is n bliksimpie,
maar ons sal hom wen.

Darren, I dicovered something that I doubt you will believe

Max EGT for a Rotax 914 is 950 deg celcuis
Makes a person think, doesn't it?

I would love to get the oil tests done, can only have an advantage.
I will be at Wagtail on Tuesday, get the samples and get them to you. I am more than
willing to pay for such a service.
Thank you for offering.

Pierre

[Magnifan]

Hi Pierre, my Rotax 914 runs at around 780 degrees, so not that much lower than tour Subaru.

[MPL Pilot]

The time came for the UFO to fly again this week, Johan has been doing some more test flights. All seem
to be in order and I should be able to start with the conversion soon.

I have upload a video clip on youtube from the past months footage made with my cell phone.

Search for "UFO RSA" or follow the link.
http://www.youtube.com/watch?v=HljKCWrx48M

Fly safe

[Wagtail]

Congrats are in order


Pierre flew in the UFO for the tirst time on Friday. Well done, excellent landing.

[Low Level]

Well done to all you guys. Glad somebody took the punch, and persevered, otherwise a pretty good gyro would most propably gathered dust somewhere and became an expensive hoenderhok.

[Gyronaut]

Congratulations Pierre and Johan! Well perservered. Hope you have many happy hours of safe flight!