Inaccurate aircraft performance

[skippydiesel]

To all aircraft dreamers out there;

 

PRODUCT WARNING!

 

The sport aircraft industry, never seems to bashfully about putting out ridiculously inflated claims for their aircraft's performance. Unless verified by an uninterested third party, treat all claims as highly suspect.

 

 

[turboplanner]

To all aircraft dreamers out there;PRODUCT WARNING!

 

The sport aircraft industry, never seems to bashfully about putting out ridiculously inflated claims for their aircraft's performance. Unless verified by an uninterested third party, treat all claims as highly suspect.

What aspects are you concerned about?

 

 

[skippydiesel]

What aspects are you concerned about?

Its not a concern, more of an observation derived from years of reading inflated claims about sport aircraft performance.

 

It is to be expected that a manufacturer/sales team will endeavour to cast their product in the 'best light" . All to often this marketing "understanding" is abused by highly improbable claims - particularity (but not exclusively) of high speed cruise, take-off, climb and range performance.

 

As an example - It might be worth checking out the wide range of light aircraft powered by the ubiquitous Rotax 912 ULS (100 hp). It is just not credible that a larger, heavier aircraft can outperform a lighter, slipperier aircraft fitted with the same engine, however there are a host of very sexy looking models that claim just that. There are a small number of Rotax 912 ULS powered aircraft that have had their performance independently verified. One such is VH-SGS built & modified by Robin Austin. Compare his world class performance with the unverified claims of so many others.

 

In my humble view, if an aircraft performance claim can not be supported by impartial testing/test data, the potential customer should view such claims with a very high degree of suspicion.

 

 

[winsor68]

Its not a concern, more of an observation derived from years of reading inflated claims about sport aircraft performance.It is to be expected that a manufacturer/sales team will endeavour to cast their product in the 'best light" . All to often this marketing "understanding" is abused by highly improbable claims - particularity (but not exclusively) of high speed cruise, take-off, climb and range performance.

As an example - It might be worth checking out the wide range of light aircraft powered by the ubiquitous Rotax 912 ULS (100 hp). It is just not credible that a larger, heavier aircraft can outperform a lighter, slipperier aircraft fitted with the same engine, however there are a host of very sexy looking models that claim just that. There are a small number of Rotax 912 ULS powered aircraft that have had their performance independently verified. One such is VH-SGS built & modified by Robin Austin. Compare his world class performance with the unverified claims of so many others.

 

In my humble view, if an aircraft performance claim can not be supported by impartial testing/test data, the potential customer should view such claims with a very high degree of suspicion.

Couldn't have said it bloody better!!! 100hp is 100hp in OZ as well as USA. Except.........

 

 

[skippydiesel]

There was quite a detailed flight test in Kitplanes magazine a couple of years back.

When was the last time "Kitplanes" did a negative report (in whole or part) on a USA manufactured aircraft ?????

 

 

[skippydiesel]

Arion Aircraft, LLCTheir 200hp Lightning will be flying shortly. It will be interesting to see how that performs!

Its soooo like the Yanks to solve all problems by just adding more ponies up front - I know nothing about the Lightning but a jump from a Jab 3300 (107 -120 hp) to a 200 hp donk? - can it even resemble the original aircraft??

 

 

[flyvulcan]

Its soooo like the Yanks to solve all problems by just adding more ponies up front - I know nothing about the Lightning but a jump from a Jab 3300 (107 -120 hp) to a 200 hp donk? - can it even resemble the original aircraft??

Skippy, the Lancair line started with the Lancair 200, then 235, 320, 360, ... Evolution, including adding more hp is not necessarily a bad thing.

 

The Lightning is also evolving. It started with the Jab3300 and is now going through the O320, O340... evolution. Cruise speed has been demonstrably improved with the increased hp so for those who want a little more speed to get from a to b, that helps them. Perhaps some builders simply want better runway performance or better climb performance. This is where the hp really helps.

 

In your quote above, what is your actual concern about the Lightning? Are you concerned that the manner in which the Lightning is evolving by adding larger engines is compromising safety in any way? Are you concerned that the Lightning structure may not be up to the task of handling the extra weight/cruise speeds etc.? Could you please elaborate?

 

If you have no concerns about the Lightning, why submit posts with negative connotations in a thread about the Lightning? As you say, you know nothing about the Lightning. Perhaps your Product Warning is not warranted or appropriate in this thread. If it is, I’d be curious to know what claims by Arion Aircraft about their Lightning have been demonstrated as being false or not achievable since I’ve just bought one based on information provided to me by Arion (plus a number of local builders as well, one of whom is on his 8th I think it is).

 

 

[skippydiesel]

Skippy, the Lancair line started with the Lancair 200, then 235, 320, 360, ... Evolution, including adding more hp is not necessarily a bad thing.....................................................................................................................................Arion Aircraft about their Lightning have been demonstrated as being false or not achievable since I’ve just bought one based on information provided to me by Arion (plus a number of local builders as well, one of whom is on his 8th I think it is).

Hi Flyvulcan - I think you may misunderstand the thrust of my comment - I have developed what I relive to be a well founded scepticism when it comes to ANY sport aircraft manufacturers performance claims for their product. I know there are those that publish conservative claims for their aircraft but they are very much in the minority (could be the Lightning is one of these).

 

Adding Power; Of course putting a bigger engine/more hp out front will tend to reduce ground role & increase climb rate and max cruise speeds. If this be what you want & can afford, go for it! For myself, I enjoy flying for the sake of it, I am occasionally envious of the trip time achievable by something small with a big engine but then remind myself I had twice the time in the air, for half the (ULP) fuel burn and probably 1/3 or less of the acquisition cost.

 

Regarding comments made by owners of aircraft -

 

• Very few owners are going to tell you about their aircraft's "short comings" Face it, we have a huge financial/time and emotional investment in our pride & joy, the last thing we are going to do is highlight its failure to perform as per the manufacturers claims.
   
   
  
• Most owners do not have the calibrated equipment with which to test their aircraft performance, so they base their observations on "indicated" at the time with little reference to temperature, altitude, attitude, fuel flow, load, etc etc - not saying they are wrong, just biased.
   
   
  

 

 

 

 

[Blueadventures]

What aspects are you concerned about?

Generalised comments that are not specific to the thread aircraft should be removed from this and any other similar threads and re-posted on an appropriately titled (new) thread. I agree with comments but sometimes when posted on a thread they do not respect the threads goal. PS I have owned an aircraft previously that does not go close to the advertised cruise speeds and I inform people about this. And I'm totally happy with the aircraft I have now. Cheers

 

 

[skippydiesel]

Blue Adventure "Generalised comments that are not specific to the thread aircraft should be removed from this and any other similar threads and re-posted on an appropriately titled (new) thread. I agree with comments but sometimes when posted on a thread they do not respect the threads goal. PS I have owned an aircraft previously that does not go close to the advertised cruise speeds and I inform people about this. And I'm totally happy with the aircraft I have now. Cheers

 

Hi Blue, I draw your attention to the opening question in this thread;

 

Rhtrudder "Dreaming about buying a lighting, all the numbers look impressive, 150kn cruise on a jabi 6 , anyone with any experience can tell me if these figures are true"

 

In the interest of those of us who have dreamt/fantasised about aircraft ownership, I believe my cautionary observation regarding the lack of advertising scruples employed by a large segment of the Sport Aircraft manufacturing industry, to be helpful advice.

 

 

[Blueadventures]

Blue Adventure "Generalised comments that are not specific to the thread aircraft should be removed from this and any other similar threads and re-posted on an appropriately titled (new) thread. I agree with comments but sometimes when posted on a thread they do not respect the threads goal. PS I have owned an aircraft previously that does not go close to the advertised cruise speeds and I inform people about this. And I'm totally happy with the aircraft I have now. CheersHi Blue, I draw your attention to the opening question in this thread;

 

Rhtrudder "Dreaming about buying a lighting, all the numbers look impressive, 150kn cruise on a jabi 6 , anyone with any experience can tell me if these figures are true"

 

In the interest of those of us who have dreamt/fantasised about aircraft ownership, I believe my cautionary observation regarding the lack of advertising scruples employed by a large segment of the Sport Aircraft manufacturing industry, to be helpful advice.

I read that the comments on this thread about inacurate aircraft performance is referring to aircraft other than the 'Lightning' and my belief is that those pieces of comment should be on a dedicated titled forum. Say named "Important information to be consider by anyone planning to purchase an aircraft kit, etc."

 

 

[turboplanner]

I read that the comments on this thread about inacurate aircraft performance is referring to aircraft other than the 'Lightning' and my belief is that those pieces of comment should be on a dedicated titled forum. Say named "Important information to be consider by anyone planning to purchase an aircraft kit, etc."

On the other hand, if it was just an aerated thought bubble, you wouldn't want to publish it anywhere.

 

 

[skippydiesel]

I read that the comments on this thread about inacurate aircraft performance is referring to aircraft other than the 'Lightning' ....................."

I am not sure I understand this comment but just to be clear - my advise is to be sceptical about ALL performance claims for ALL aircraft, until the researcher is confident that the claims have been or can be independently verified & are repeatable.

 

 

[jetboy]

Dreamers should do their own research, however there are a few common misunderstandings about performance figures etc.

 

For instance, Dynearo might get more from a Rotax 912 because they use a custom muffler

 

All the Zenair line have airspeeds qouted as IAS and if you read the construction plans there is no external static pressure port.....

 

gives better readings 5 - 10 kts

 

USA planes often quoted in mph - sounds better than the kts version

 

Takeoff / landing distance done at less than MAUW, without 50' obstacle clearance distance, grass or paved surface not quoted.

 

these are all 'legitimate' sales talk

 

 

[peter]

My Onex performs as well or better than the Sonex published data, have been pleasantly surprised that the data “claimed“ matches the real world performance.

 

 

[Blacksheep]

I see cruise speeds quoted without any reference to altitude or even if they mean ias or tas. It might be correct in that the aircraft really can cruise at that speed but it might not be at altitudes most people fly at. Its something to keep in mind when reading the advertisements for sure.

 

 

[David Isaac]

I agree totally with the caution that Skippy diesel is suggesting.

 

I have been vocal in the past for the same reason when I see some absurd claims for takeoff distance that do NOT use the standard professional aviation convention quoting take off distance to a 50’ obstacle clearance ... after all that is the real distance; or

 

Absurd claims to stall speeds that can never be achieved without any reference as to whether there is any ‘position error’, or whether it is IAS, or CAS; and

 

Absurd claims to STOL performance that state the damn thing can also cruise at ‘120 knots’ with absolutely no reference to the turbulence penetration limitations. References to cruise speed that would have to be at WOT to be anywhere near possible, certainly not any reference to cruise speed at say 75% power with a relevant fuel burn rate; and

 

Then there is the old chestnut ‘G’ structural rating when many of the claims I have seen are NOT a ‘rating’ but more a structural limit ... which is something you don’t want to be anywhere near.

 

It is almost that since LSA aircraft came out, much of the sales hype disregarded professional avaition convention just to BS to uneducated purchasers.

 

 

[KRviator]

I wouldn't say "all" manufacturers pad out their performance claims... Vans is well-known for being accurate with their claims. For example, in my -9, I cruise at 2400RPM which works out to around 55% TAS'ing 143-145 KTAS. Vans does use SMPH for their performance figures, but after converting to knots, I am exactly where they say I should be for a lightweight RV-9 at 55%.166SMPH / 144.2KTAS.

 

IF, however, you are looking at a brand-new/new-ish manufacturer, then yes, I would be somewhat sceptical. The internet is a wonderful tool for calling out BS claims, and when you get interested in a particular plane, a night or two with Google will usually produce enough meaningful performance data to show whether or not the manufacturers claims can be trusted.

 

Ignore the 38LPH indicated fuel flow. This was during a fuel-flow sensor validation flight after installing the new Rotec TBI. After 2 hours flying laps around the Hunter, it was 24.5LPH, measured.

 

 

 

[skippydiesel]

I wouldn't say "all" manufacturers pad out their performance claims... Vans is well-known for being accurate with their claims. For example, in my -9, I cruise at 2400RPM which works out to around 55% TAS'ing 143-145 KTAS. Vans does use SMPH for their performance figures, but after converting to knots, I am exactly where they say I should be for a lightweight RV-9 at 55%.166SMPH / 144.2KTAS.IF, however, you are looking at a brand-new/new-ish manufacturer, then yes, I would be somewhat sceptical. The internet is a wonderful tool for calling out BS claims, and when you get interested in a particular plane, a night or two with Google will usually produce enough meaningful performance data to show whether or not the manufacturers claims can be trusted.

 

There are honest manufacturers out there, however they are the exception. The willingness to claim a "silk purse when supplying a sows ear" is not just limited to the newer manufacturers - I have read some astonishing advertising claims from some well established sport aircraft makers and vice versa.

[facthunter]

IF a plane is not a clean design going faster by adding horsepower is an experience in rapidly diminishing returns. Most more powerful motors are heavier and you then need weight in the tail to balance the extra weight in the nose. This gives a more adverse distribution of mass fore and aft which can affect the spin characteristics of the plane markedly. The design should have the wing moved further forward (often not really achievable),rather than using weights. Jabiru engines are relatively light for HORSEPOWER. But have a smaller prop option, without re drive. Thrust is what a plane needs to overcome drag. Converting HP to thrust brings a few extra things into the equation, especially for draggy planes. Going above say 150 knots, is another world of design, drag, structural and flutter considerations. You need to know a lot more about design to safely operate there. Nev

 

 

[APenNameAndThatA]

Its not a concern, more of an observation derived from years of reading inflated claims about sport aircraft performance.It is to be expected that a manufacturer/sales team will endeavour to cast their product in the 'best light" . All to often this marketing "understanding" is abused by highly improbable claims - particularity (but not exclusively) of high speed cruise, take-off, climb and range performance.

As an example - It might be worth checking out the wide range of light aircraft powered by the ubiquitous Rotax 912 ULS (100 hp). It is just not credible that a larger, heavier aircraft can outperform a lighter, slipperier aircraft fitted with the same engine, however there are a host of very sexy looking models that claim just that. There are a small number of Rotax 912 ULS powered aircraft that have had their performance independently verified. One such is VH-SGS built & modified by Robin Austin. Compare his world class performance with the unverified claims of so many others.

 

In my humble view, if an aircraft performance claim can not be supported by impartial testing/test data, the potential customer should view such claims with a very high degree of suspicion.

Wouldn't you just take along a GPS for the sales pitch flight?

 

 

[facthunter]

I would have thought most would have one. (GPS) The location of the static source is the most likely cause of indicated Airspeed error. If it's inside the fuselage it reads slower at the lower end and faster at the top end. (Just what you want if you are trying to embellish the "apparent" performance). Nev

 

 

[skippydiesel]

APenname: "Wouldn't you just take along a GPS for the sales pitch flight?"

 

I could be wrong but the GPS will only give you ground speed. Tell you nothing about density altitude, power settings & fuel flows, not sure about climb performance either.

 

I find that the claimed endurance/distance possible @ econo cruise power against maximum fuel available, often gives the game away and where published max level speed @ max cruise with fuel consumption (for the nominated engine) which seem improbable.