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C-ARF Ultra Flash build Thread + Video

Old 05-15-2013, 11:30 AM
  #2976
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Default RE: C-ARF Ultra Flash build Thread + Video

Quote:
ORIGINAL: IFlyEm35


Quote:
ORIGINAL: Beavis



Quote:
One of the benefits of having an aft CG is a lower stall speed so that would make sense.
Could you please elaborate on that basic concept (for the non-aerodynamicist)? I always thought that, with regard to weight, the stall speed was affected only by the overall weight and not by the CG as well. Of course, it appears that I thought wrong...

Thank you in advance.

I'm writing from my phone so I'll give you the Cliff's Notes version and update it once I get to a computer.

You are correct. Weight affects stall speed. Your CG is in front on your center of lift. This is why the nose drops when the wing stalls. So when in normal flight, to offset the nose dropping the tail produces a tail down force. This force adds to the overall weight the wings need to support. So move the CG forward and an increased tail down force is required to offset it. This results in the higher wing loading and increased stall speed.

To expand:

Stalling is a component of reaching the critical AOA (Angle of Attack). AOA is increased with a forward CG because the increased distance between the center of pressure (lift) and the CG. This requires the tail to produce more downforce to keep the nose from dropping. That downforce then has to be overcome with more lift. To create more lift AOA is increased.

Think of a teeter totter. One end is the nose of the aircraft, the other is the tail and the pivot point is the center of lift. If your CG is is ON the center of lift, the pivot point, both ends of the teeter toter or very light and easy to move. This would be unstable in the world of aviation. But would have the slowest stall speed. So the CG has to be moved towards the front of the plane. (So when the aircraft is in a stalled state the nose drops so the aircraft can recover.) This causes the nose side of the teeter toter to come down. To combat that we have the horizontal stabilizer. This creates the taildown force to lift the nose.

As that CG moves closer to the nose end of the teeter toter it take more and more pressure on the opposite end to counter act that. As pressure is added the more force is being applied as the pivot point (i.e. lift). So in a nustshell, the more weight the wings have to support the higher the AOA, the higher the stall speed.

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Old 05-15-2013, 12:29 PM
  #2977
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Default RE: C-ARF Ultra Flash build Thread + Video


IFlyEm,

Thank you for the expansion and helpful pictures. Expanding on my previous note as well, correct me if I’m wrong, but it appears that basically what you are saying is that a more forward CG increases the load factor. As you probably know better than me, load factor is a well-established variable defined as:

n = L/W, where:

n = load factor
L = lift
W = weight

It is also well established that the load factor affects stall speed through the formula:

Vst = Vs √n, where:

Vst = stall speed
Vs = stall speed in straight, level flight
√n = square root of the load factor

This is also why the stall speed increases during high load maneuvers, such as high bank turns and certain aerobatic moves.

Wow, look at all that math in RCU!

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Old 05-15-2013, 12:42 PM
  #2978
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Default RE: C-ARF Ultra Flash build Thread + Video

No stall....different sites, different models. Its not the model.

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Old 05-15-2013, 01:17 PM
  #2979
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Default RE: C-ARF Ultra Flash build Thread + Video


Quote:
ORIGINAL: Beavis


IFlyEm,

Thank you for the expansion and helpful pictures. Expanding on my previous note as well, correct me if I’m wrong, but it appears that basically what you are saying is that a more forward CG increases the load factor. As you probably know better than me, load factor is a well-established variable defined as:

n = L/W, where:

n = load factor
L = lift
W = weight

It is also well established that the load factor affects stall speed through the formula:

Vst = Vs √n, where:

Vst = stall speed
Vs = stall speed in straight, level flight
√n = square root of the load factor

This is also why the stall speed increases during high load maneuvers, such as high bank turns and certain aerobatic moves.

Wow, look at all that math in RCU!


Load Factor is the ratio of Lift to Weight. Essentially it is a G-Force. So in straight and level unaccelrated flight the load factor is +1. So if the weight goes up the lift needs to be increased. But doesn't directly indicate an increase in load factor. As long as they are equal the load factor is +1.

Load Factor increases as you increase lift. I.E. if you develop 4000lb of lift and the craft weighs 2000 lbs you are acheiving a load factor of +2.0. When pulling out of a dive or a tight turn and you have an accelerated stall it is when the lift (created by AOA) exceeds the Critical AOA and a stall is achieved.

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Old 05-16-2013, 07:01 AM
  #2980
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Default RE: C-ARF Ultra Flash build Thread + Video

I, for one, am enjoying this thread immensely. It just so happens I've been having trouble landing my Ultra lately. I'm flying out of a fairly short grass strip and I've been using flaps only - no crow. My problem? I'm having trouble judging stall speed. I've been flying model aircraft my whole life and this is a first. This was precipitated by the aircraft dropping a wing in the pattern (turning from base to final). It's a miracle I didn't destroy it, but since then I don't trust it a bit. Obviously it was my fault for going too slowly but I got no indication that I was nipping at the verge of a stall and REALLY felt like I had plenty of speed for the approach.

It's very obvious that it's purely a matter of personal preference whether to use crow or not but I just went into my DX18 program and reactivated the crow that I used when this aircraft was a classic. I'm going to see what it think of it on the Ultra. I'm hoping crow will be more predictable in the pattern.

(For those that may wonder, my CG is biased to the rear - probably in the 235mm area, and I've been using 85mm full flap setting).
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Old 05-16-2013, 08:17 AM
  #2981
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Default RE: C-ARF Ultra Flash build Thread + Video

We fly from a 290' strip, and It's no problem flying the UF in and out even in calmer conditions. Personally I've never felt the UF was going to stall and you get sooo much information from the feel of the aeroplane through the sticks.

I've had some contact about where the balance is measured, so I did this on an UF I'm building now...

Dw
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Old 05-16-2013, 08:35 AM
  #2982
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Default RE: C-ARF Ultra Flash build Thread + Video

Quote:
ORIGINAL: Dave Wilshere

We fly from a 290' strip, and It's no problem flying the UF in and out even in calmer conditions. Personally I've never felt the UF was going to stall and you get sooo much information from the feel of the aeroplane through the sticks.

I've had some contact about where the balance is measured, so I did this on an UF I'm building now...

Dw
I agree. I find it interesting how many people are having issues with the model stalling. Mine is about as heavy as they come as I have every tank imaginable, smoke, and the monster battery required for the kero start Kingtechs. I set up for slow flight and crawl the model around. Not once has the wing even burbled. I am currently on a trip and won't be home for a couple days but I'll check my CG when I get home. I am sure its located right infront of the main gear legs. The nose wheel is EXTREMELY light as seen in my video when it's taxiing.
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Old 05-16-2013, 10:05 AM
  #2983
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Default RE: C-ARF Ultra Flash build Thread + Video

I'm guessing that the differences are just due to people's setups and flying styles but seeing as there seem to be 2 distinct groups of experiences with this model makes me wonder, do CARF only have one mould/jig for the wing? If there are more than one, is it possible that one of them is different to another?

Are all Ultra Flashes the same?
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Old 05-16-2013, 10:15 AM
  #2984
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Default RE: C-ARF Ultra Flash build Thread + Video

Quote:
ORIGINAL: siclick33

I'm guessing that the differences are just due to people's setups and flying styles but seeing as there seem to be 2 distinct groups of experiences with this model makes me wonder, do CARF only have one mould/jig for the wing? If there are more than one, is it possible that one of them is different to another?

Are all Ultra Flashes the same?
i really dont think there is 2 sets of wings , but if you really want to find out , then have Dave fly your plane , and if they fly different , then yes

if not you buy Dave A BEER
Who is up to the challenge ???

I'll put up the first beer if i am wrong .

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Old 05-16-2013, 10:16 AM
  #2985
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Default RE: C-ARF Ultra Flash build Thread + Video


Quote:
ORIGINAL: siclick33

I'm guessing that the differences are just due to people's setups and flying styles but seeing as there seem to be 2 distinct groups of experiences with this model makes me wonder, do CARF only have one mould/jig for the wing? If there are more than one, is it possible that one of them is different to another?

Are all Ultra Flashes the same?
+1, I have thought of this. Too many people having problems just to dismiss it
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Old 05-16-2013, 10:16 AM
  #2986
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Default RE: C-ARF Ultra Flash build Thread + Video

Quote:
ORIGINAL: IFlyEm35

Quote:
ORIGINAL: Dave Wilshere

We fly from a 290' strip, and It's no problem flying the UF in and out even in calmer conditions. Personally I've never felt the UF was going to stall and you get sooo much information from the feel of the aeroplane through the sticks.

I've had some contact about where the balance is measured, so I did this on an UF I'm building now...

Dw
I agree. I find it interesting how many people are having issues with the model stalling. Mine is about as heavy as they come as I have every tank imaginable, smoke, and the monster battery required for the kero start Kingtechs. I set up for slow flight and crawl the model around. Not once has the wing even burbled. I am currently on a trip and won't be home for a couple days but I'll check my CG when I get home. I am sure its located right infront of the main gear legs. The nose wheel is EXTREMELY light as seen in my video when it's taxiing.
Iflyem35, I find it interesting that you totally agree with DW. Didn't I read somewhere on this thread that you are using crow? So were you having issues before the crow? Or no issues either before or after? Or neither. If neither, why then the crow?
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Old 05-16-2013, 10:25 AM
  #2987
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Default RE: C-ARF Ultra Flash build Thread + Video

Another interesting common denominator.. Has anyone had a wing drop with crow? Or is every problem reported with flaps only
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Old 05-16-2013, 11:09 AM
  #2988
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Default RE: C-ARF Ultra Flash build Thread + Video

So you balance yours right side up?


Quote:
ORIGINAL: Dave Wilshere

We fly from a 290' strip, and It's no problem flying the UF in and out even in calmer conditions. Personally I've never felt the UF was going to stall and you get sooo much information from the feel of the aeroplane through the sticks.

I've had some contact about where the balance is measured, so I did this on an UF I'm building now...

Dw
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Old 05-16-2013, 12:19 PM
  #2989
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Default RE: C-ARF Ultra Flash build Thread + Video

Quote:
ORIGINAL: Dave Wilshere

We fly from a 290' strip, and It's no problem flying the UF in and out even in calmer conditions. Personally I've never felt the UF was going to stall and you get sooo much information from the feel of the aeroplane through the sticks.

I've had some contact about where the balance is measured, so I did this on an UF I'm building now...

Dw
I've had a classic Flash stall on flight #1 and it was 100% my fault. I got the plane too slow and then pulled the nose up, which induced a tip stall.

Bluebus, I've never had a wing drop with crow, even at walking speed.
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Old 05-16-2013, 06:43 PM
  #2990
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Default RE: C-ARF Ultra Flash build Thread + Video


Quote:
ORIGINAL: siclick33
...do CARF only have one mould/jig for the wing? If there are more than one, is it possible that one of them is different to another?

Are all Ultra Flashes the same?
IIRC one of the posts in this thread talks aboout a few sets of moulds due to the popularity of the plane.
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Old 05-16-2013, 07:41 PM
  #2991
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Default RE: C-ARF Ultra Flash build Thread + Video


Quote:
ORIGINAL: mitchilito

Quote:
ORIGINAL: IFlyEm35

Quote:
ORIGINAL: Dave Wilshere

We fly from a 290' strip, and It's no problem flying the UF in and out even in calmer conditions. Personally I've never felt the UF was going to stall and you get sooo much information from the feel of the aeroplane through the sticks.

I've had some contact about where the balance is measured, so I did this on an UF I'm building now...

Dw
I agree. I find it interesting how many people are having issues with the model stalling. Mine is about as heavy as they come as I have every tank imaginable, smoke, and the monster battery required for the kero start Kingtechs. I set up for slow flight and crawl the model around. Not once has the wing even burbled. I am currently on a trip and won't be home for a couple days but I'll check my CG when I get home. I am sure its located right infront of the main gear legs. The nose wheel is EXTREMELY light as seen in my video when it's taxiing.
Iflyem35, I find it interesting that you totally agree with DW. Didn't I read somewhere on this thread that you are using crow? So were you having issues before the crow? Or no issues either before or after? Or neither. If neither, why then the crow?

I only flew the model once with flap only. I do not recall how slow I flew it on the maiden. I put the crow in because I didn't care for the nose down attitude the airplane assumed with the flaps. My personal preference is the crow attitude. But I never felt the model has been anything but solid.
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Old 05-16-2013, 10:54 PM
  #2992
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Default RE: C-ARF Ultra Flash build Thread + Video

Checked and its not 1st April

You think a company like CARF make different shape wings...can't drink my morning coffee I'm smiling so much. This thread really has lost it!
All these people having trouble...
Of the many many hundreds of UF flying I've heard of...none, except on here this last two weeks. Yes there will be a few people who weren't sure, who now come forward, but I'm telling you there is no issue with this aeroplane. Its the best all around sports jet yet.
We can't see the radio set ups, how the model was built, there can be a HUGE difference in weight. I don't land my model with lots of "heavy" fuel still on board-I'm sure its not so nice 'heavy' but I've flown it in enough conditions like last Sunday which was a horrid wind and never had the Uh oh moment landing.
This is a sports jet capable of near 300mph and flies out of a 290' strip no problem. It has one of the biggest speed ranges I know of.
In England there are a lot of pilots flying UF's and I've yet to be contacted about "stalling" I'd say we are 50-50 on CROW, no CROW of people I can think of. Some people land just fine without and some just fine with. Ali started using it as he prefered the feel on landing, I've never heard him say because it was wing dropping. There is nothing to stop you having either set up. In my mind if just one or two people don't stall/flick their UF's in without CROW and a tonne of flap it proves the model is fine...or are ALL these people exceptional pilots??
Geee I'm all for looking at the problem and trying to help but this "Problem" is really getting me...pi**sed.

I've said it before and I'll say it one last time. I've flown a lot of Ultra Flashes, so from the various moulds and I've never seen an issue, its a complete bolt from the blue.

Anyone wants my input please pm as I'm going to stay away from this keyboard punching thread for a few days

Dave
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Old 05-17-2013, 12:30 AM
  #2993
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Default RE: C-ARF Ultra Flash build Thread + Video

Dave, I agree with you 100%. With my Ultra Flash, it never tip stalled regardless of speed. That plane did not have crow.
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Old 05-17-2013, 05:47 AM
  #2994
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Default RE: C-ARF Ultra Flash build Thread + Video

While it is possible that there are manufacturing tolerances that will cause some variances, i feel that considering the posibility of several moulds that could have huge differences is a bit overboard, I still believe there is nothing wrong with the design, can't understand why that has been implied, I still believe the problem is in the set-up, and with all due respect, just because an individual did not experience the "dropping wingtip" does not mean it did not hapoen, come on! there is actual video evidence, why woudl people lie about it?
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Old 05-17-2013, 06:02 AM
  #2995
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Default RE: C-ARF Ultra Flash build Thread + Video

Many, if not most, aircraft will drop a wing if allowed to stall. Just because I let it happen once is not a reflection on the aircraft. I believe the Flash, both CF and UF (I've owned both) are FINE aircraft - and very honest.

When I say I'm having trouble feeling my way around the stall It's certainly no reflection on this fine machine. Let's not take any of this personally!
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Old 05-17-2013, 06:25 AM
  #2996
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Default RE: C-ARF Ultra Flash build Thread + Video

Mitch, don't know if you are replying to my comments, if so, not intended to be directed to you or any specific individual.
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Old 05-17-2013, 03:29 PM
  #2997
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Default RE: C-ARF Ultra Flash build Thread + Video


Quote:
ORIGINAL: Dave Wilshere

Checked and its not 1st April

You think a company like CARF make different shape wings...can't drink my morning coffee I'm smiling so much. This thread really has lost it!
All these people having trouble...
Of the many many hundreds of UF flying I've heard of...none, except on here this last two weeks. Yes there will be a few people who weren't sure, who now come forward, but I'm telling you there is no issue with this aeroplane. Its the best all around sports jet yet.
We can't see the radio set ups, how the model was built, there can be a HUGE difference in weight. I don't land my model with lots of ''heavy'' fuel still on board-I'm sure its not so nice 'heavy' but I've flown it in enough conditions like last Sunday which was a horrid wind and never had the Uh oh moment landing.
This is a sports jet capable of near 300mph and flies out of a 290' strip no problem. It has one of the biggest speed ranges I know of.
In England there are a lot of pilots flying UF's and I've yet to be contacted about ''stalling'' I'd say we are 50-50 on CROW, no CROW of people I can think of. Some people land just fine without and some just fine with. Ali started using it as he prefered the feel on landing, I've never heard him say because it was wing dropping. There is nothing to stop you having either set up. In my mind if just one or two people don't stall/flick their UF's in without CROW and a tonne of flap it proves the model is fine...or are ALL these people exceptional pilots??
Geee I'm all for looking at the problem and trying to help but this ''Problem'' is really getting me...pi**sed.

I've said it before and I'll say it one last time. I've flown a lot of Ultra Flashes, so from the various moulds and I've never seen an issue, its a complete bolt from the blue.

Anyone wants my input please pm as I'm going to stay away from this keyboard punching thread for a few days

Dave
No, Ruiz. I was actually trying to make DW feel better
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Old 05-18-2013, 12:19 AM
  #2998
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Default RE: C-ARF Ultra Flash build Thread + Video

Quote:
You think a company like CARF make different shape wings...can't drink my morning coffee I'm smiling so much. This thread really has lost it!
In full scale aviation I have seen highly professional companies release a whole batch of faulty parts on more than one occasion. One of the faulty batch of parts that I saw meant that when the component failed (which it frequently did) the engine couldn't be started, so all of the aircrew were taught how to change this part, and spare parts and tools were carried on the aircraft at all times. If it can happen to a full scale aviation manufacturer, with all the QC and regulations that they are bound by, then I don't see why CARF can be considered immune from ever making a mistake.

It was unlikely to be the case and, as I stated in my previous post, the few problems that people are experiencing are probably due to setup and flying style, but it was possible which is why I asked the question. If Dave says that all the moulds are fine then that's my question answered.
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Old 05-18-2013, 08:15 AM
  #2999
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Default RE: C-ARF Ultra Flash build Thread + Video

Quote:
ORIGINAL: Dave Wilshere

Checked and its not 1st April

You think a company like CARF make different shape wings...can't drink my morning coffee I'm smiling so much. This thread really has lost it!
All these people having trouble...
Of the many many hundreds of UF flying I've heard of...none, except on here this last two weeks. Yes there will be a few people who weren't sure, who now come forward, but I'm telling you there is no issue with this aeroplane. Its the best all around sports jet yet.
We can't see the radio set ups, how the model was built, there can be a HUGE difference in weight. I don't land my model with lots of ''heavy'' fuel still on board-I'm sure its not so nice 'heavy' but I've flown it in enough conditions like last Sunday which was a horrid wind and never had the Uh oh moment landing.
This is a sports jet capable of near 300mph and flies out of a 290' strip no problem. It has one of the biggest speed ranges I know of.
In England there are a lot of pilots flying UF's and I've yet to be contacted about ''stalling'' I'd say we are 50-50 on CROW, no CROW of people I can think of. Some people land just fine without and some just fine with. Ali started using it as he prefered the feel on landing, I've never heard him say because it was wing dropping. There is nothing to stop you having either set up. In my mind if just one or two people don't stall/flick their UF's in without CROW and a tonne of flap it proves the model is fine...or are ALL these people exceptional pilots??
Geee I'm all for looking at the problem and trying to help but this ''Problem'' is really getting me...pi**sed.

I've said it before and I'll say it one last time. I've flown a lot of Ultra Flashes, so from the various moulds and I've never seen an issue, its a complete bolt from the blue.

Anyone wants my input please pm as I'm going to stay away from this keyboard punching thread for a few days

Dave
Hey Dave, I don't think this is at all like the threads when people are bashing a product, I'm sure just about all of us love our Ultra Flashes. I think some are like myself "pre-maiden" , & are just afraid to F'ing it up, so trying to cross every T & dot every I.. I for one feel that hearing these experiences have improved my chances of success. Like the saying goes- "smart men learn from their mistakes, wise men learn from others"
Jay
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Old 05-18-2013, 08:39 AM
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Default RE: C-ARF Ultra Flash build Thread + Video

Jay, you have to do something really stupid to stall the Flash/Ultra Flash. I know because I did something really stupid to cause the stall. At the speed and AOA I was flying, any plane would stall. That was flight #1 and I put 500 more flights on it and never stalled it again.
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