TarDevil
Well-Known Member
Fortunately for Peter, in lieu of thorough testing, the meager power available assures a fairly level climb attitude.
10/23 Raptor Video
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You guys are beating up an old topic - Engine power. We know why the power is soft and have talked about it plenty. Since PM has said he will not be altering these issues now, I think we could let the topic lie with zero losses to our collective knowledge or wisdom.
The cooling system has had some modest changes made to it:
Then we get to stability and control. This flight was early in the day, no thermals and little wind. Yet it displayed combined Pitch-Roll-Yaw cycles that look similar to what occurred on the first flight. Roll and pitch and yaw still look coordinated to me, just of smaller magnitude, which might have more to do with increased stability in pitch and yaw, or might be mostly due to a calmer air mass. Maybe the interaction has more to do with heavy ailerons and the pilot's hand, but the cycles seem to be there. Without adding channels for input positions and then downloading flight data and analyzing it, we can not be sure. I am betting this becomes more interesting when PM gets some straight and level flight.
Billski
The cooling system has had some modest changes made to it:
- Improved air outlet from the cowling, which should increase cooling system air flow some;
- Increased heat sink, which adds weight and slows down the warmup, but changes heat rejection not at all;
- Addition of a poorly configured radiator that can not move enough air to substantially improve heat rejection;
Then we get to stability and control. This flight was early in the day, no thermals and little wind. Yet it displayed combined Pitch-Roll-Yaw cycles that look similar to what occurred on the first flight. Roll and pitch and yaw still look coordinated to me, just of smaller magnitude, which might have more to do with increased stability in pitch and yaw, or might be mostly due to a calmer air mass. Maybe the interaction has more to do with heavy ailerons and the pilot's hand, but the cycles seem to be there. Without adding channels for input positions and then downloading flight data and analyzing it, we can not be sure. I am betting this becomes more interesting when PM gets some straight and level flight.
Billski
I crudely measured 20 seconds from 5-90 knots at takeoff. Seemed better acceleration to me. Of course he could lift off at 80 but no need. Reports on YouTube say gear down is high drag.
It was the other way around. It always needed left aileron. The airplane wants to roll right. He put the tab on the left wing and it is bent up. It appears to have not been too much.
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I was with you all the way until the (1.327)2. Whilst we could argue about whether to square or some other number I thought instead to review the numbers on my plane:
1. Slow flight Gear Down 110KCAS @55% (150HP) (~3600# weight)
2. Max cruise Gear Up 165KCAS @80% (250hp)
The numbers are very close to Raptor so, like my plane, I would expect 165KCAS at S/L at 80% for the Raptor too. At 25,000 feet 165KCAS = 243KTAS which is the a great number if (BIG IF) the Raptor can make 80% at altitude. The fuel burn at 80% for the Raptor is likely to be 16GPH and for the P210 (ROP) is about 28GPH. So the Raptor could win here as the TSIO520 is an ROP fuel hog at high power in order to stay cool. The Diesel, not so. However as pointed out, 7GPH at those speeds and weights is simply dreaming.
So I don't agree the Raptor could ever see 194KCAS with this power, however even if it only attains 165KCAS it will still be fast if those turbos can be made to work at alt.
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flywheel1935
Well-Known Member
heeeeeeres Johnny !!!!
flyboy2160
Well-Known Member
In the latest episode at about 6:20 he describes how, in the first flight, the canard stalled right at rotation and continued to alternately stall along with the main wing stalling. But moving the cg forward fixes this.......and over to you in the booth, Marc......
rv6ejguy
Well-Known Member
I'd expect a 10 inch deep HX to have nearly 100% effectiveness at these low airflow rates. No surprise and he's learned nothing useful here.
Yep. Needs to measure flow rate and determine how many more to install.
ImperfectSense
Member
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He keeps using the term "heat being radiated out" in the end of the video but then completely ignores the fact that, indeed, that could be all it is? Meaning there may not be actual _airflow_ happening. Made me twitch every time he'd make the assumption he had airflow just because he had heat transmission. Obviously at high speeds rolling down the runway he had airflow, but when he was sitting still on the ground with everything shut off, he was still insisting he must have airflow from a "breeze". But if you look at the telltales hanging off the stab they are completely stationary. No breeze _at all_. It's a minor point and doesn't really matter in terms of the airworthiness of the design (much), but it still just makes me cringe.
A MEAT thermometer? Oh the humanities!
I'd probably have done the same thing
I'd probably have done the same thing
Marc Zeitlin
Exalted Grand Poobah
Sigh. _IF_ there were any main wing stalls going on (which there most certainly are not, unless PM has a different definition of stall than the aerodynamic community as a whole) then moving the CG forward would help to prevent main wing stalls. Aside from stability concerns, preventing main wing stall (deep stall) is the second (and possibly MORE important) reason for the rear CG limit location on canard type aircraft.
If the Raptor had had a main wing stall, the plane would have crashed, given the low altitude at which he was flying and the experiences of everyone else that's had a deep stall in a canard type aircraft.
As far as the CANARD airfoil stalling, yeah, no. It isn't. As I pointed out in my comments about his first flight, since he's rotating at a speed ABOVE the slowest speed he was able to fly, and since there's no discernable drop in the nose of the plane, he can't be stalling (at 1G) at a speed above the lowest speed the plane can fly. PM's looking at relatively stiff and too long tufts made out of the wrong material, seeing some reverse flow near the trailing edge, and thinking that that implies that the airfoil is stalled, because there's a bit of separation going on. I'll just say that his lack of aerodynamic understanding is fairly robust.
On my plane, with a Roncz canard on a COZY MKIV (but folks have seen this on GU canards on VE's and LE's and COZY III's as well) you can fly through some rain and have water bead up on the TE of the elevator and just sit there. You're flying at 100 - 140 KIAS, but there are water blobs just dancing around about 1/2" fwd of the TE of the elevator. WTF, you think. All it means is that there's a bit of separation there and a small amount of reverse flow. Price of doing business with these airfoils. It is obviously NOT an indication of canard stall, as I can fly my plane at the rear CG limit down to about 61 KIAS.
PM has never had either the canard or the main wing stall on him in the Raptor, and he should be extremely happy about that fact. If the canard stalled on rotation, the nose would have slammed back down onto the ground, possibly breaking something. And if the main wing had stalled, particularly only on one side, as he surmises, he'd have been sideways and rolled up in a ball on the ground.
A few little facts to know and compare to what was presented in the video:
Aerodynamics:
Then we get to evaluate if the canard was on the verge of stall at rotation speed. Well, maybe a canard at 10-12 degrees AOA plus a deflected flap could approach stall there. We saw no big pitch down, so I doubt he actually got to stall. So what will moving the CG forward do to this? It will add load to the canard, either raising the speed required at which the foil AOA plus elevator position can make lift equal to load or require still more elevator angle to rotate at the same speed. Did either of those happen?
Heat Rejection:
Billski
Aerodynamics:
- Airplanes fly in steady state when weight applied to each of foil is balanced by lift produced by the foil. If the loads do not balance, the airplane will accelerate in the direction of the excess force.
- Airfoils stall when their angle of attack exceeds their critical AOA.
- Shifting CG forward adds load to the canard and reduces load on the main wing.
Then we get to evaluate if the canard was on the verge of stall at rotation speed. Well, maybe a canard at 10-12 degrees AOA plus a deflected flap could approach stall there. We saw no big pitch down, so I doubt he actually got to stall. So what will moving the CG forward do to this? It will add load to the canard, either raising the speed required at which the foil AOA plus elevator position can make lift equal to load or require still more elevator angle to rotate at the same speed. Did either of those happen?
Heat Rejection:
- Heat removed by a heat exchanger can be estimated two ways - Knowing the change in heat in the coolant and knowing the change in heat in the effluent. In both cases, the rate of heat removed (Hdot) is the product of specific heat capacity of the fluid (Cp) times mass airflow of the fluid (mdot) times change in temperature of the fluid (dT). Yes, Hdot = Cp*mdot*dT. Maybe you saw this in high school chemistry as H = Cp*m*dT. Here we made it into rate of heat flow and rate of mass flow;
- Heat lost from the coolant is equal to heat added to the air, so if you have both, you can even check your work here;
- We can look up Cp of coolant and of ambient air, and we have an estimate of dT for the air but not for the coolant. We have no estimate of the mass flow rate of either air or coolant. We can not even guess with any accuracy at the heat rejection of the new HX with the available data;
- If we had those temperature probes attached to the coolant inlet and outlet pipes, we could however find out if we were getting any coolant temperature change. A good target on coolant dT is 10F. If the coolant was loosing 10F going through the HX, it might have been working well. To me that result would justify some method of estimating mdot. And if the coolant shows the same temperature at the inlet and at the outlet, there is approximately zero heat being rejected, validating the estimates of some of us that air flow will be very small through this HX.
Billski
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I think the previous flight had pilot induced oscillations that exceeded intended rotation angle and nibbling at stall. Mentioned by Velocity on the YouTube comments. The CG was too close to neutral so the forward move tamed the PIO. He was above the normal 1g stall speed at all times. But stall nibbling can occur above stall speed with rapid stick movements. (stall is AOA not just speed)
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Marc Zeitlin
Exalted Grand Poobah
But they were incorrect, as discussed previously. The motion of the plane was NOT what happens during a canard stall. I believe that they misjudged what they were seeing in the video.
MAYBE the CG was too close to the NP - some folks are making that judgement based on a stabilized GoPro movie in a plane piloted by someone not familiar with flying canards and who was almost certainly inducing a fair bit of PIO's, which I see in MY plane when someone not familiar with canards flies it, and which I've tested to the limits of the performance envelope. I would not be categorical about the CG location, NP location, or the relation between the two - we are operating with almost zero actual information here. Moving the CG forward would certainly make the plane more stable in pitch, but it's not clear that it was unstable on the first flight.
Since he was not just above the 1G stall speed, but substantially above the 1G stall speed, the small elevator movements, which change the effective AOA of the canard by a degree or two, would not be anywhere near enough to cause an instantaneous canard stall. Since there were no nose drops (bobbing, it's usually called) of the nose with a constant elevator position, I will say that I'm 99.99999% sure that neither of the flying surfaces on the Raptor aircraft has ever stalled (yet).
See above. The stick movement would need not only to be rapid enough to occur faster than the inertia of the aircraft would allow the plane to move, but also large enough to actually cause an AOA change above the stall AOA. This did not happen - the elevator TE movements during the pitch oscillations seen in the first flight were minuscule - almost imperceptible. That's not causing canard stall, when 25% above the 1G stall speed.
Yeah, I would think stall "bobbing" would be much longer frequency. I did think the PIO elevator movements were quite noticeable on the first flight. And the attitude instrument was going wild in pitch.
It is likely it was mostly PIO on the first flight from unfamiliarity.
I suppose it could be that he learned to tame his PIO after only that one minute first flight.
The rear CG limit can be explored more later to determine if that was a factor or if it was PIO.
It is likely it was mostly PIO on the first flight from unfamiliarity.
I suppose it could be that he learned to tame his PIO after only that one minute first flight.
The rear CG limit can be explored more later to determine if that was a factor or if it was PIO.
flywheel1935
Well-Known Member
Seems to me, and possibly others? that unless a new YT video is featured of the Raptors latest mods, then there is very little to comment on. Having followed progress with both interest and dismay for over 2 years its apparent that nothing anybody suggests will ever be implemented, so I've got to the point not to bother anymore. Seems the designer is using a meat thermo, if that's the case then the Raptor is definitely going to be 'rare' !!!! see what I did there, it's got that boring, I'm gone.
poormansairforce
Well-Known Member
TarDevil
Well-Known Member
Yeah, kinda recycling at this point.
That Audi is performing exactly as we suspected and the project can't move forward with that powerplant.
If next week he announces the purchase of a mid time TSIO-550, it's a new game.
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Flight 3 just went live.
flightaware.com
Looks like a nice circuit with 130 knot groundspeed on downwind recorded and up to 860 ft/min climb rate. Maybe tried gear up?
Definitely improving.
N352TD Flight Tracking and History 08-Dec-2020 (KVLD-KVLD) - FlightAware
Track N352TD flight from Valdosta Rgnl to Valdosta Rgnl
Looks like a nice circuit with 130 knot groundspeed on downwind recorded and up to 860 ft/min climb rate. Maybe tried gear up?
Definitely improving.
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