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Aero News Network Video - Terrible Raptor 1st Flight Review

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BBerson

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His recent sealing up of the 2" gap in the radiator plenum should be his most effective cooling improvement since the last flight. It should also have some silicone fabric flex gasket gap seal. It looked like a complex , unsealed, welded aluminum vane director was installed to curve flow into the radiator. Not needed, I think. It needs a sealed duct.
 
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TFF

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Tweaks like different antifreeze mixes, water wetter, spaybars really only help when you are marginally redline on temperature. Most of the time in this situation you are just trying to get on the good side of the gauge, with a proven setup. This thing right now is just a boiler. At least he kept his eye on the gauge or he should add steam pistons. Cold outside air and hot inside air are a weather system. Hot and cold air do not want to mix. If you don’t lead that air out, it will not leave.
 

Alessandre

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Correct me the experts if I am wrong, but by the logic if an engine cannot cool by running statically with full power then it is not safe to fly, or it is allowed an extra static heating hoping that in flight by the greater air flow this problem solved?
 

BJC

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In most conventional E-AB type aircraft, the cooling comes from airflow, through the engine and or radiator cowling, generated by forward speed. Propeller “blast” doesn’t provide much cooling, so forward speed is needed to cool at power levels required for flight.


BJC
 

BBerson

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It's the ram dynamic pressure from forward flight needed. It didn't work on the test flight because he had a 2" gap above the radiator allowing pressure to leak past instead of through the radiators.
 

Wanttaja

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Correct me the experts if I am wrong, but by the logic if an engine cannot cool by running statically with full power then it is not safe to fly...
I think a lot of pushers are in that boat. And the problem with the Raptor is not that it can't cool statically at full power, it's that it can't cool statically at idle.

Even tractor aircraft have trouble cooling on the ground, occasionally. The root section of the propeller isn't that efficient for pushing air back. That's why they use "test clubs" for ground testing rather than normal propellers.

Ron Wanttaja
 

berridos

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I am totally amazed by the v channel in front of the landing gear hole. When i saw it in the previous video, it was like spotting an ovni, with a thoussand questionmarks in my head.
 

Alessandre

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I think this dyno wasn't broken, the performance of the aircraft was worthy for 175hp. The acceleration and climb rate don't lie.
 

rv6ejguy

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I think this dyno wasn't broken, the performance of the aircraft was worthy for 175hp. The acceleration and climb rate don't lie.
In answering a YT comment today, Peter is still convinced that he's making over 300hp. 14 days ago, it was 400hp. Only an engine dyno would be able to quantify the truth here.
 

consciousness256

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... I calculate he's around 293hp now from the latest run.
Just curious, the previous power estimate is around 200-225hp from the acceleration data right? I didn't really watch the video, but I wonder where that extra 70ish hp came from. What that extra turbo finally removed?

Also, what's the material of those tufts? Seems not quite like yarn tufts that were shown in many other aircraft videos. Surprisingly long and rigid?
 

pictsidhe

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In answering a YT comment today, Peter is still convinced that he's making over 300hp. 14 days ago, it was 400hp. Only an engine dyno would be able to quantify the truth here.
Well, it would in my world. But the harsh reality is that when a dyno doesn't verify Peter's estimated power, the only plausible explanation is that it is broken.
I look forward to Peter finding and fixing whatever is causing enough drag to destroy the performance.
 
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175hp/251trq at 3,900rpm on the dyno 🤔. Dyno must be broken...
I notice that even back then he was only expecting 320 h.p. from that engine/turbo setup... how on earth did the expected numbers jump to 400 and even 450 h.p.? Did his horsepower numbers just conveniently go up whenever his gross weight went up?
 

wsimpso1

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Correct me the experts if I am wrong, but by the logic if an engine cannot cool by running statically with full power then it is not safe to fly, or it is allowed an extra static heating hoping that in flight by the greater air flow this problem solved?
While some airplanes might cool adequately at high power while tied down, I would not make that a criteria for a liquid cooled airplane engine. Here is why:

Static ground tests (without a fan) have little cooling flow, so are basically not cooling on the ground. A ground run will show how quickly the system warms up without rejecting heat to ambient air. Remember that you are warming the engine metal, coolant and radiator, and other systems that can sink heat (like the fuel) being warmed by the hot coolant.

High speed taxi with good airflow will see temperature rise rate (dT/dt) decrease as heat starts going into the ambient air from the various HX. In liquid cooled engines, the temperature should look like it is heading for a level off between 192 F (where the thermostat opens) and somewhere below coolant boiling point. Correcting the max to a 100 F day is standard for US cars. You might correct for 120 F if you expect to operate in the desert SW, GCC, Australia. That would be my criteria for acceptable takeoff - the temps are flattening out during the roll and look like they will stay in bounds during climb.

If instead during the high speed taxi, the temperature is headed for temps higher than coolant boiling point, the system will overheat if power is left in. Safe flight criteria should drive one to reject the takeoff under these conditions. Proceeding with the takeoff leaves you with the choice to continue climb and likely destroy the engine or pull power back to save the engine, then fly at reduced power while low and slow back to the runway. UGH.

The ground data we have seen does look like an insulated system - like there is little to no heat rejection, just raising temps of engine and cooling system. If it is cooling at all, it is giving no indications of leveling off at any reasonable temperature. I would not consider Raptor acceptable for flight until the cooling is greatly improved. There are other issues...

Billski
 

pictsidhe

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I notice that even back then he was only expecting 320 h.p. from that engine/turbo setup... how on earth did the expected numbers jump to 400 and even 450 h.p.? Did his horsepower numbers just conveniently go up whenever his gross weight went up?
His hp numbers went up whenever he thought he added more.

Cooling air. The exit is very close to the prop, it will be experiencing sugnificant suction. Pressure wont be much higher than in flight. The intake is much slower air during static runs. If I were to take a guess, I'd say he may have 2/3 airflow static compared to 100kts. That should be enough for 75% power.

I notice that he seems to need 50% power for high speed taxi. Seems a lot to me.
 
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rv6ejguy

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I notice that even back then he was only expecting 320 h.p. from that engine/turbo setup... how on earth did the expected numbers jump to 400 and even 450 h.p.? Did his horsepower numbers just conveniently go up whenever his gross weight went up?
They are all uneducated guesses. Anyway, if Raptor flies again, and it really has 320hp, I'll be expecting to see a 1300 fpm ROC like an SR22 can do at the same weight.
 

rv6ejguy

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Just curious, the previous power estimate is around 200-225hp from the acceleration data right? I didn't really watch the video, but I wonder where that extra 70ish hp came from. What that extra turbo finally removed?

Also, what's the material of those tufts? Seems not quite like yarn tufts that were shown in many other aircraft videos. Surprisingly long and rigid?
Peter did some more tuning and thinks he gained some more hp recently.
 
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