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Don Dykins book

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air.guerner(at)wanadoo.fr
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Posted: Wed Jan 30, 2008 12:21 am Post subject: Don Dykins book

Hi  all, 

I  have just read Don Dykins book « Understanding the aerodynamics of your  Europa aircraft » and I am puzzled by what I read in the “Prototype flight  test performance” section.<?xml:namespace prefix = o ns =  "urn:schemas-microsoft-com:office:office" /> 

 Figure 1 on page 15 shows that you need  more power to fly at a given airspeed at altitude than at sea level. I first  thought it was a typo, but page 18 confirms this assertion: “more HP is required  to fly at a given speed at 10,000ft than at sea level”.   

The  typical light aircraft cruises about 5 to 10 percent faster at  <?xml:namespace prefix = st1 ns =  "urn:schemas-microsoft-com:office:smarttags" />10000 ft than at sea level using the  same power, and you can verify this with your own Europa as  well. 

So  Don Dykins is wrong. Unless he is talking about indicated airspeed. In that  case, talking about performance, this is  nonsense. 

I  cannot believe someone who has contributed to the design of such a wonderful  aircraft can be so wrong. Am I missing something?   

Please comment. 

  

Remi  Guerner

    [quote][b]

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craigb(at)onthenet.com.au
Guest

Posted: Wed Jan 30, 2008 3:28 am Post subject: Don Dykins book

If you  consider the fact that you need more power or a longer ground run to take  off at high temps or lower pressures (higher density  altitude)

 then  Don's assertions are correct. Consider also  that some aircraft were  supercharged during world war 2 only to delay the onset of "coffin  corner"

 and  allow for a higher service ceiling. Well thats my 2 cents  worth.

  

 Craig

 [quote]   --

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m.j.gregory(at)talk21.com
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Posted: Wed Jan 30, 2008 3:35 am Post subject: Don Dykins book

Hello Remi,  

   

Yes, the airspeed axis on page 15 Figure 1 is labelled "VEASKTS", standing for Equivalent Airspeed in knots, which is a more technically precise term than Indicated Airspeed for aerodynamicist's calculations.  For practical purposes, they may be treated as equal for the flight envelope of the Europa.  

   

The reason why you need more horsepower at altitude for a given IAS is that, for a given efficiency, the engine is providing thrust to equal the same drag (which is dependent on IAS) but the True Airspeed is greater, so the actual distance moved in a given time is greater.  Work = Force x Distance; Power = Work/time.  The engine is therefore having to do more work in a given time at the same IAS at altitude, but this is more than offset by the gain in TAS, so cruising at a given TAS requires less horsepower at altitude.  

   

I do not believe Don Dykins is wrong, and I do not agree that it is nonsense to talk about performance in terms of indicated airspeed.  As I understand it, he is showing his calculations of aerodynamic performance and comparing them with the results of flight tests, where IAS is measured.  

   

It would be interesting to know how the latest VP propellers compare in efficiency with his working assumption of 80%.  

   

Best regards  

   

Mike        

  

From: owner-europa-list-server(at)matronics.com [mailto:owner-europa-list-server(at)matronics.com] On Behalf Of Remi Guerner

 Sent: 30 January 2008 08:12

 To: Europa-List Digest Server

 Subject: Don Dykins book  

  

     

Hi all,  

I have just read Don Dykins book « Understanding the aerodynamics of your Europa aircraft » and I am puzzled by what I read in the “Prototype flight test performance” section.  

 Figure 1 on page 15 shows that you need more power to fly at a given airspeed at altitude than at sea level. I first thought it was a typo, but page 18 confirms this assertion: “more HP is required to fly at a given speed at 10,000ft than at sea level”.   

The typical light aircraft cruises about 5 to 10 percent faster at  10000 ft than at sea level using the same power, and you can verify this with your own Europa as well.  

So Don Dykins is wrong. Unless he is talking about indicated airspeed. In that case, talking about performance, this is nonsense.  

I cannot believe someone who has contributed to the design of such a wonderful aircraft can be so wrong. Am I missing something?   

Please comment.  

   

Remi Guerner  

  [quote] [b]

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mikenjulie.parkin(at)btin
Guest

Posted: Wed Jan 30, 2008 6:30 am Post subject: Don Dykins book

Craig,

  

 I am not sure that is correct.  'Coffin  Corner' describes the area of the flight envelope where stalling speed meets the  critical mach no.  This is a problem with high flying aircraft such as the  U2.  I don't think that extra power would help here.

  

 regards,

  

 Mike

  

 do not archive.

 [quote]   ---

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craigb(at)onthenet.com.au
Guest

Posted: Wed Jan 30, 2008 12:16 pm Post subject: Don Dykins book

Sure  my use of the term "coffin corner" may not be correct, but it is a  simmilar situation is it  not??

 If the  approach to coffin corner is caused by a lack of power rather than a design  limitation then it would be, wouldnt it? Say like trying to fly your Europa with  60hp

 at  high altitude, you would end up in the same situation, can't go slower or I'll  stall, can't go faster not enough power. Some of the heavier 912ul powered  europa are flat out

 at  around 120kts arent they, yet the design is good for about 165-175  kts.

  

 craig 

 [quote]   --

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mikenjulie.parkin(at)btin
Guest

Posted: Wed Jan 30, 2008 4:14 pm Post subject: Don Dykins book

Craig,

  

 What you are talking about is a stall - plain an  simple.  It is nothing to do with the "Coffin Corner".  Please see [url=http://en.wikipedia.org/wiki/Coffin_corner_(aviation]http://en.wikipedia.org/wiki/Coffin_corner_(aviation[/url])  

  

 regards,

  

 Mike

 [quote]   ---

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air.guerner(at)wanadoo.fr
Guest

Posted: Thu Jan 31, 2008 1:08 am Post subject: Don Dykins book

Mike Gregory  wrote:



"Yes, the airspeed axis  on page 15 Figure 1 is labelled "VEASKTS", standing for Equivalent Airspeed in  knots ..........I do not believe Don Dykins is wrong, and I do not agree that it  is nonsense

to talk about performance in terms of indicated  airspeed. "

  

 Mike,

  

 I fully  understand that. But again when talking about cruise performance, what the  builder owner or pilot of the Europa is interested in is True Air Speed, not  Indicated Airspeed. This is why I said this is nonsense.

 Fortunately I  did not pay the 5 British Pounds for the book, as I just borrow  it!

 Best regards

 Remi 

 



    [quote][b]

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