24 Apr 2024, 08:54 [ UTC - 5; DST ]
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Username Protected
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Post subject: Re: Raptor Aircraft 5 Seat Pressurized 3,600 NM Range Die  Posted: 21 Jul 2020, 00:55 |
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Joined: 02/25/16
Posts: 287
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Location: Tupelo, MS
Aircraft: 182R
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Username Protected wrote: Distance from the end of the runway to the windsock is 2500ft. This thing is going to need a 10000ft runway for testing It is interesting - he referenced that they were targeting 85kts for initial tests. That's going to start to push any accelerate-and-stop distances at his 5000' runway. He's basically at 75kts by midfield...and the faster speeds will eat more runway, so 75->85 will be...sporty. Losing some weight would help...but as mentioned, that'll be a tough one at this point in the project.  EDIT - and for extra irony, one would want the AC off for max power (and to minimize non-essential systems) during testing anyway... 
The thing is heavier than a damn Piper Mirage... He should've built a bare bones prototype to prove his projected performance numbers. Would've saved him a lot of time and money.
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Post subject: Re: Raptor Aircraft 5 Seat Pressurized 3,600 NM Range Die Posted: 21 Jul 2020, 01:14 |
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Joined: 12/28/17
Posts: 773
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Company: Bellanca Aircraft
Location: Washington, OK
Aircraft: 17-30A
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Username Protected wrote: Another major problem he has ignored is his pitot tube placement. What's wrong with where the pitot tube is?
Major disparity between airspeed reading and GPS on his takeoff roll. They should be the same on the ground, not 10+ mph difference.
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Post subject: Re: Raptor Aircraft 5 Seat Pressurized 3,600 NM Range Die Posted: 21 Jul 2020, 03:46 |
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Joined: 11/03/08
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Location: Peachtree City GA / Stoke-On-Trent UK
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Username Protected wrote: When are the test pilots come to fly the plane?
Mike as soon as one of them is diagnosed with something projecting weeks left to live ?
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Post subject: Re: Raptor Aircraft 5 Seat Pressurized 3,600 NM Range Die Posted: 21 Jul 2020, 07:58 |
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Joined: 05/01/14
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Username Protected wrote: They should be the same on the ground, not 10+ mph difference. Wind impacts the pitot tube on the ground as well. Also, between being on wheels and ground effect, the relative wind angle could be different on the ground vs in flight. Then there is simply miscalibration. Who knows, with this project there’s no limit to what problems may be.
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Post subject: Re: Raptor Aircraft 5 Seat Pressurized 3,600 NM Range Die Posted: 21 Jul 2020, 08:43 |
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Joined: 08/26/15
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Username Protected wrote: They should be the same on the ground, not 10+ mph difference. Wind impacts the pitot tube on the ground as well.
Guys, guys, guys... both of you are forgetting some private pilot 101 stuff.
Read the METARs that I posted on this thread yesterday and look closely at the wind sock (2:56, 8:02, and 10:26).
Mike, you're forgetting about the difference between true airspeed and indicated airspeed. Ground speed and indicated airspeed should most definitely not be the same at 1000' and ISA +12. (But it shouldn't be over 10 knots for those conditions.)
Yes, bad pitot tube placement (installation error) can't make an airspeed read high, it can only make it read low. Bad static port placement can do either (but again, I don't think his static port is the problem because his altimeter is fairly steady the whole time the airplane is making power- the altimeter really only moves after he chops the power).
Matt, wind would have been my first guess too but it turns out there wasn't much or any wind (calm on the METAR and light and variable at best on the windsock).
And I think we're all forgetting some pretty obvious troubleshooting when airspeed is either reading so much less than ground speed or apparently lagging by so much: leak checking the pitot system (not the static system, the pitot system) and opening the water drain.
Last edited on 21 Jul 2020, 09:34, edited 1 time in total.
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Post subject: Re: Raptor Aircraft 5 Seat Pressurized 3,600 NM Range Die Posted: 21 Jul 2020, 08:43 |
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Joined: 02/28/17
Posts: 1214
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Location: Panama City, FL
Aircraft: Velocity XL-RG
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Username Protected wrote: Wind impacts the pitot tube on the ground as well. Also, between being on wheels and ground effect, the relative wind angle could be different on the ground vs in flight. Then there is simply miscalibration. Who knows, with this project there’s no limit to what problems may be. Looks like a calm day so there shouldn't be much difference between airspeed and groundspeed. What I find curious is that he loses about 40' of altitude on the first run. Assuming there isn't a 40' difference along the runway (been a while since I flew in there), then that would indicate the static port is in a high pressure area. But that would result in a lower than actual airspeed reading. Static port placement can be a PITA. 5 years flying and I'm still futzing with mine trying to get it right. 
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Post subject: Re: Raptor Aircraft 5 Seat Pressurized 3,600 NM Range Die Posted: 21 Jul 2020, 10:35 |
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Joined: 05/01/14
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Username Protected wrote: Static port placement can be a PITA. 5 years flying and I'm still futzing with mine trying to get it right. That’s why more formal flight testing programs usually use a static cone/trailing cone.
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Post subject: Re: Raptor Aircraft 5 Seat Pressurized 3,600 NM Range Die Posted: 21 Jul 2020, 13:07 |
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Joined: 02/28/17
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Username Protected wrote: Static port placement can be a PITA. 5 years flying and I'm still futzing with mine trying to get it right. That’s why more formal flight testing programs usually use a static cone/trailing cone.
A static cone is good for determining your true altitude and static pressure, but it's doesn't help find a location on the airframe for a permanent static port.
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Post subject: Re: Raptor Aircraft 5 Seat Pressurized 3,600 NM Range Die Posted: 21 Jul 2020, 19:44 |
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Username Protected wrote: I imagine that Peter’s method of pitot/static calibration ... will be innovative and worthy of discussion.  I had harped on him about pitot/static stuff last year - and if I recall he stated the airplane has no static ports at all. I think he had mentioned he just dumped a static line into that front hatch area and left it open (the same hatch area that was sucking the bungee'd front hatch door open during his "runs"), and like everything "he's ok with that"...
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Post subject: Re: Raptor Aircraft 5 Seat Pressurized 3,600 NM Range Die Posted: 21 Jul 2020, 20:08 |
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Joined: 09/21/13
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Username Protected wrote: I imagine that Peter’s method of pitot/static calibration ... will be innovative and worthy of discussion. I had harped on him about pitot/static stuff last year - and if I recall he stated the airplane has no static ports at all. I think he had mentioned he just dumped a static line into that front hatch area and left it open (the same hatch area that was sucking the bungee'd front hatch door open during his "runs"), and like everything "he's ok with that"...
Genius - it'll never ice over!
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Post subject: Re: Raptor Aircraft 5 Seat Pressurized 3,600 NM Range Die Posted: 21 Jul 2020, 20:37 |
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Joined: 08/24/13
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Username Protected wrote:
I had harped on him about pitot/static stuff last year - and if I recall he stated the airplane has no static ports at all. I think he had mentioned he just dumped a static line into that front hatch area and left it open (the same hatch area that was sucking the bungee'd front hatch door open during his "runs"), and like everything "he's ok with that"...
Alternate static all the time. Fits with all the other "engineering"
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