# Raptor Composite Aircraft

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#### pictsidhe

##### Well-Known Member
I did calcs on hp based on the acceleration and static thrust tests months months ago and came up with around 225-250- far short of his 400ish hp estimates.

The gear leg attachments look mighty flexible to me and that prop got pretty close to the ground there from the video.

One question for my US friends here, can someone qualify for insurance without a minimum number of flight hours in the previous year? I've never seen Peter mention anything about flying to stay current though I might have missed it.
Some months ago I too came up with low 200s for horsepower. I have a recollection of using a different method to you. It's notable that those of us here who can calculate this sort of stuff, are all getting similar numbers to each other, yet wildly different to Peter's ever rising hp.

Bill Clapp was giving him some test pilot lessons in his aircraft. Peter has at least a few recent hours.
When he first moved to Valdosta, he was talking about maybe getting the resident test pilot to test it out. I guess Bill Clapp declined that.

#### jet guy

##### Well-Known Member
I had a look at the new video - looks like 30s acceleration to 90kts - jetguy should be able to give us a reasonably accurate HP value from this.

Yeah that run matches very closely with the acceleration observed earlier. It looks to take about 32 seconds to reach his 90 knot rotation. In the previous episode it takes about 22 seconds to get from 20 knots to 79 knots.

In both cases I am starting to count only when I hear his engine at full power, and stopping when you hear him back off the power.

I spoke earlier about doing a more detailed calculation:

The simple reality is that there is nothing new and very little guesswork involved in performing very accurate aircraft performance analyses. This is always done when designing a clean sheet airplane and setting performance targets, as well as extracting those unknown numbers for a competitor aircraft.
So I have worked up a calculator that lets you compute the drag polar of any airplane for which you have accurate data, such as from a POH. In the calculator I use the SR22 data to find the parasite drag coefficient Cdo, which then lets us put together the entire drag polar for the airplane. And also takeoff performance, cruise performance etc.

The same method can be used for any other airplane POH and I have run also the TBM 850 and Bonanza A36. It's very accurate.

Just a couple of notes on my earlier post, where I brought out some of the analysis methods: I had found a somewhat highish figure for Oswald Efficiency factor e, so it turns out that the Continental engine in the Cirrus actually makes a little more power than book. When I looked into it, I found that the new Contis are certified for rated power plus 5 percent, minus 0 percent. So they actually average a little more power than the factory number.

Using a figure of plus 3 percent, which works out to about 320 hp, we get an Oswald number of 0.85, which is very much in line with what we would expect [the C182 is 0.84, a technical paper on Oswald number here].

Another article I found is about prop efficiency in Bonanzas in cruise, which is about 0.9, a very good propulsive efficiency. A couple of good articles from this Bonanza fellow, about the IO550 power and the prop efficiency.

Btw, Prof Rogers has a lot of interesting technical articles on his website, including a DIY angle of attack indicator which would be dandy for flight testing experimental aircraft.

So here is the calculator with the Cirrus SR22 example worked out. The second sheet has the takeoff performance analysis. I also use the Raptor as a worked example, for an aircraft for which accurate data is not known. The method lets us compute all the drag and thrust parameters as we did with the Cirrus, based only on the demonstrated aircraft performance in its acceleration runs. You can use this with any POH for any aircraft.

Finally we estimate engine power, using the prop efficiency calculated for the Cirrus at 0.7 rotation velocity. This is the analytic method used when you are trying to predict takeoff performance, and want to get an average thrust number for the entire run. Plugging in the observed takeoff roll numbers from both the latest video and the earlier one gives pretty much the same results.

The engine power comes out to about 230 to 240 hp, which is more than I expected, but this is because of the high rotation speed, and thus the higher drag.

Another interesting point is the fact that he needs to get to 90 knots before he can even rotate. This is because his rotation angle is severely limited by prop clearance. Peter mentions that he gets about 5 to 7.5 degrees, but this is only half of typical rotation angle of 15 degrees.

This has a very big impact on takeoff. This plane, at this weight at least, could rotate at about 77 knots if he had enough prop clearance. This is a disaster. It means a takeoff roll of 30 seconds plus and about 2,500 ft distance, at least. And this is with one guy on board and light fuel. If he loads the airplane even a little we may be looking at a 100 knot rotation, and a 3,000 foot run...and that's before we even take hot and high conditions into account.

This airplane is the epitome of failure. Any reasonable person would be greatly concerned at this stage and would call it off and start building the second prototype with lighter weight, a well proved engine with the required power, and all the improvements that are required in the aerodynamics, flight controls etc.

That's what a smart person would do. He or she would take these valuable lessons learned as an important stepping stone in reaching the ultimate goal of creating a decent airplane, and addressing all of the glaring shortcomings that are now absolutely telling you it's time to quit and start over.

About the Drag Calculator, if anyone would prefer an earlier Excel format let me know. Also any feedback or questions appreciated.

[Edit: the drag calculator may open on the second sheet for takeoff performance. you can click on the sheet tab at bottom to get to the drag analysis page.]

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#### Wild Bill

##### Well-Known Member
I think the main gear leg movement is a combination of things.
The geometry of the gear leg itself looks like it would be prone to twisting.
I think this has been discussed. A little twist between the gear leg pivot and the “bend” will look like a lot down at the wheel.
The leg pivot bolt is not a precision Machined fitted part. This was shown in at least one of the videos.
Add in some braking Issues and it’s not surprising that there is movement.

#### rbarnes

##### Well-Known Member
Peter mentions that he gets about 5 to 7.5 degrees, but this is only half of typical rotation angle of 15 degrees.
Not necessarily for a canard. It's one of the things that turns me off on them. They have very flat takeoff and landing attitudes. Paul B mentions it in his canard training class he took at Velocity and recently wrote about

#### BJC

##### Well-Known Member
HBA Supporter
I think the main gear leg movement is a combination of things.
Anyone here ever watched the movement in most Cessna gears? RV gears?

Granted, they are operated at lower speeds, but the move around quite a bit.

BJC

#### rv6ejguy

##### Well-Known Member
Anyone here ever watched the movement in most Cessna gears? RV gears?

Granted, they are operated at lower speeds, but the move around quite a bit.

BJC
The rear LEGS flex on plenty of aircraft but not the support structure as seen here. He already had a partial failure on the pivot area in the "wild ride" segment.

#### TFF

##### Well-Known Member
No insurance is required in the US.
Airports may require it for hangar leases. You don’t want to hand prop a plane and have it run into a king air; it’s all on you. You don’t want to engine out on someone’s house.

Being a business, it’s probably insured some way. He could also umbrella policy himself. Right now helicopter insurance has gotten so crazy, I bet most are flying naked or just can’t get it. It put the company I worked for out of business because no one would write a policy. It’s what happens when a couple of billionaires crash helicopters and they have to pay 100 million out to a family.

#### Wild Bill

##### Well-Known Member
Wittman style gear legs do flex and move all over the place.
Flat steel gear Cessnas don’t have a lot of fore-aft movement. At least on fixed gear.
Here on the raptor I guess the question is can it handle the loads. It looks pretty robust but some parts have already come lose on it. Didn’t look like critical components though.
As it wears some and the hammering effect of gear movement continues, it may if nothing else cause some excess wear on those parts.
He’s put extra cameras on the gear to see what is going on for some reason.
It looks pretty clear that leg flex alongside excess clearance is where it’s at.
He also may be on the brakes as Justin mentioned it being easy to inadvertently apply brakes.
From Peters perspective it may be that the gear movement results in a undesirable feeling in the seat.

#### cheapracer

##### Well-Known Member
Log Member
I think the main gear leg movement is a combination of things.
Yeah, a 3400lb aircraft combined with a 200lb pilot.

#### pictsidhe

##### Well-Known Member
I think the main gear leg movement is a combination of things.
The geometry of the gear leg itself looks like it would be prone to twisting.
I think this has been discussed. A little twist between the gear leg pivot and the “bend” will look like a lot down at the wheel.
The leg pivot bolt is not a precision Machined fitted part. This was shown in at least one of the videos.
Add in some braking Issues and it’s not surprising that there is movement.
Peter showed a gear leg camera on the last video. It shows the top of the leg is moving a lot, too. Most of the movement is thereforefrom a flexible mounting.
He told Justin he just drilled a long slightly oversized hole, and put a bolt through. No bushings. I don't know if he put some extra plies and any bracing on the layup. We saw a lot of very poorly designed hardpoints for the controls...

#### Rik-

##### Well-Known Member
What is he up to now, 6 takeoff and landings?
Can he log them in his log book? He’s daytime VFR current

#### Turd Ferguson

##### Well-Known Member
The rear LEGS flex on plenty of aircraft but not the support structure as seen here. He already had a partial failure on the pivot area in the "wild ride" segment.
bingo! Gear legs that double as springs flex quite a bit at the tire end but not at the attach end like Raptor is doing. The slow motion video looks b-a-d but as long as buyers are ok with it.......

#### BBerson

##### Light Plane Philosopher
HBA Supporter
Would the composite gear leg attach mounts fail suddenly and collapse or show problems slowly?

#### rv6ejguy

##### Well-Known Member
No insurance is required in the US.
Airports may require it for hangar leases. You don’t want to hand prop a plane and have it run into a king air; it’s all on you. You don’t want to engine out on someone’s house.

Being a business, it’s probably insured some way. He could also umbrella policy himself. Right now helicopter insurance has gotten so crazy, I bet most are flying naked or just can’t get it. It put the company I worked for out of business because no one would write a policy. It’s what happens when a couple of billionaires crash helicopters and they have to pay 100 million out to a family.
So no liability insurance is required to operate aircraft in the US? Wow.

How about currency requirements outside the BAFR?

#### Turd Ferguson

##### Well-Known Member
Wittman style gear legs do flex and move all over the place.
Flat steel gear Cessnas don’t have a lot of fore-aft movement.
Both of those are Wittman's design. The round type is considered an improvement as it can absorb energy in any direction and is less likely to tear your gear mounts out. I can assure you a Cessna gear does not flex in the mounting area.

#### rbarnes

##### Well-Known Member
So no liability insurance is required to operate aircraft in the US? Wow.
How about currency requirements outside the BAFR?
Currency outside of BAFR is 3 take off and landings if you have passengers and same for night ops.. if I remember my PPL test right...
Insurance is not required by law, but pretty much every hanger or tie down spot you rent long term will require it and any FBO you park at overnight will require it but they never ask to have it on file or anything.

#### Wild Bill

##### Well-Known Member
I can assure you a Cessna gear does not flex in the mounting area.
I was referring to BJC’s post regarding movement of the axle end of the gear on the round bar style gear.
Not movement at the gear leg attachment.