fenix flight dynamics

[ha5mvo 253]

@omarsmak30 

As I said, I feel nothing. Hence I tend to dismiss reviews that tell me how right (or wrong) the plane "feels".

here are some eurocontrol figures for a very generalized ROC values. Even for ballpark values, this is way more than the  claimed 6% difference

Aircraft Performance Database > A320 (eurocontrol.int)

[Matt Webb 171]

I feel there's a little play on the work "feel" in this topic.

Quote

feel

[fiːl]

 

VERB

feels (third person present)

1. be aware of (a person or object) through touching or being touched.

   "she felt someone touch her shoulder" · 

   [more]

   synonyms:

   perceive · sense · detect · discern · make out · notice · observe · identify · be sensible of · have a sensation of · be aware of · be conscious of
2. experience (an emotion or sensation).

   "I felt a sense of excitement" · 

   [more]

   synonyms:

   experience · undergo · go through · bear · endure · suffer · be forced to contend with · know · have
3. have a belief or impression, especially without an identifiable reason.

   "she felt that the woman positively disliked her"

   synonyms:

   sense · have a feeling · get the impression · feel in one's bones · have a hunch · have a funny feeling · just know · intuit

NOUN

feels (plural noun)

1. an act of touching something to examine it.
2. a sensation given by an object or material when touched.

   "nylon cloth with a cotton feel"

   synonyms:

   texture · surface · finish · grain · nap · weight · thickness · consistency · quality · character
3. informal

   (feels)

   feelings of heightened emotion.

   "fans will undoubtedly get the feels when they see how things haven't changed" · 

   [more]

 

Edited June 2, 2022 by Matt Webb

[espent 1,396]

42 minutes ago, ha5mvo said:

@omarsmak30 

As I said, I feel nothing. Hence I tend to dismiss reviews that tell me how right (or wrong) the plane "feels".

here are some eurocontrol figures for a very generalized ROC values. Even for ballpark values, this is way more than the  claimed 6% difference

Aircraft Performance Database > A320 (eurocontrol.int)

Are those the general numbers from how an average plane flies, or is it max climb numbers?

[Pilot53 544]

I admire the OP's guts questioning the fenix A320 while requesting real world verifiable data, that's a punishable offense these days on this forum.  I hope you brought your bulletproof vest....

Edited June 2, 2022 by Pilot53

[MDFlier 2,031]

I think it was a valid question, but I don't really see where guts come into play.

I re-read this thread and everyone seems to have been cordial and non-argumentative. The question was posed in a sincere, non-inflammatory manner and the responses received were in kind. 

If he were to say "You guys are idiots because you like this plane that may in someone's opinion climb too fast". He would have received some well deserved flack.  

 

[robert young 2,897]

3 hours ago, MattNischan said:

Very much so. Pretty much every aircraft dev will tell you that they will receive downright opposing suggestions from two different pilots all the time (who, generally don't at all have exact figures), and that often pilots "absorb" (for lack of a better term) a lot of flight model differences because they're used to, well, actually flying a plane, which is a much more feel and muscle memory sort of exercise than a test pilot type of situation where exact telemetry is also important.

Generally if the pilots are in a majority agreement you know you at least hit the feel enough so that it's in that muscle memory ballpark, but even still you can be off from book figures by a decent amount. Compounding that is that book figures are themselves not hugely precise: it's what a few planes did on average on a best-possible-average type day with humans at the stick. So often you have to really divine an alternate reality that compromises between all these different inputs.

On top of all that the million pound simulators are using table lookup physics which are derived from, you guessed it, the book figures, and they effectively have zero non-normal envelope data. So that adds another layer of inexactness. But it's good enough for training purposes (because again, good pilots "absorb" these differences, and the procedures are really what is being trained in these sims).

This is an interesting subject. In many years of developing flight models, I've come across testers who though very experienced pro pilots on type, get a complete disconnect between flying the real thing and the "feel" of a flight sim. Many tend to concentrate on whether systems, procedures, autopilot and expected outcomes like climb rates, mach numbers and descent profiles etc appear to be correct while not necessarily being critical of plain, simple reaction to control inputs. I think that is often because the limited feel of consumer sim flying controls from a chair lead to a certain forgiveness or allowance for sim hardware.

A classic case recently was a commercial pilot who made a youtube video landing the MSFS default Caravan on a short runway and completely messing short finals and the flare to the point where the Caravan crashed. Instead of criticising the default flight model (which has that awful bouncing, pogo stick extreme pitch reaction to the slightest pitch input), she sort of put it down to her own incompetence. She was either unwilling to criticise the flight model or perhaps was being diplomatic and blamed herself.

In many years of developing a wide variety of sim aircraft I can recall only three actual pilots out of many who seemed to be able to translate their critical faculties from real world to the consumer sim world, and one of those is not even a commercial pilot (he is a well known member here) but whom I respect because he has an eye for very fine detail when manual aircraft handling is concerned.

For that reason I have become quite sceptical about addons that emphasise in their marketing blurb that they were thoroughly tested by pros. A case in point is a beautifully done, popular recent addon which in all respects other than manual flying is superb, but frankly it flies manually like a pig, being a real handful, clumsy, over-sensitive to the slightest input and ungainly in every axis. Larger aircraft tend to be less over sensitive and much easier to model where basic controls are concerned. But smaller aircraft are actually quite difficult to model. Though I love MSFS I don't think the default aircraft, and a lot of addon aircraft, have anywhere near acceptable basic flying characteristics, and that is not so much the sim itself, but very poor tuning of individual flight models.

Partly to blame is the very short "throw" of most consumer joysticks which make the situation even worse.

[Pilot53 544]

1 hour ago, MDFlier said:

I think it was a valid question, but I don't really see where guts come into play.

 

it was just a joke, and yes a valid question indeed.

[FrankR409 514]

5 hours ago, Bobsk8 said:

A few Airbus Airline Pilots have commented that the Fenix  flight model is very realistic. There are hours and hours of Youtube Videos that Airline A 320 Pilots of made, and this is a frequent comment that they make. 

Very good point, and I have heard the same.  I tend to have much more faith in the videos from professionals, than comments here from individuals with zero hours in an A320. Same goes for the very excellent release of the new Sting S4, developed and tested by people with many hours in a real plane.  

[JYW 2,980]

53 minutes ago, FrankR409 said:

Very good point, and I have heard the same.  I tend to have much more faith in the videos from professionals, than comments here from individuals with zero hours in an A320. Same goes for the very excellent release of the new Sting S4, developed and tested by people with many hours in a real plane.  

A professional pilot is well armed to understand and convey how their aircraft behaves through all phases of flight. However, beyond 'numbers' (which is all that some people think a FDE consists of), is a pilot necessarily skilled in measuring how accurate the transfiguration of real world aircraft behaviour into pixels moving on a screen is?    In fact, there is no such thing as accuracy in that regard - whether pixels moving on a screen feels like a real aircraft moving though the air is entirely subjective.

In that regard, I'm inclined to prefer (again subjectively) a flight model built by someone like Rob Young, above (who in case some are not aware, built some of the most applauded flight models in the business, as one half of RealAir.   RealAir Duke anyone?   RealAir Legacy?   What were they known for?  Divine flight handling characteristics.   Conversely, you have something like the SWS Kodiak, which - as beautiful as it is in visual and auditory fidelity, feels pretty gnarly and odd to fly - despite real pilots stating that it "flies right, against the numbers".

Translating the movement of an aircraft through the air into pixels moving around our screen, as part of a wonderful elaborate illusion is art not science.

Edited June 3, 2022 by JYW

[FrankR409 514]

13 minutes ago, JYW said:

 

In that regard, I'm inclined to prefer (again subjectively) a flight model built by someone like Rob Young

Yup subjective, everything you said.

[G550flyer 1,013]

6 hours ago, ha5mvo said:

So I hopped onto the Fenix bandwagon.

While the system simulation is quite impressive - on par with the FS Labs from initial impression, I keep wondering how accurate are the flight dynamics.

On initial climb for instance, I keep getting high pitch command with about 4000 f/m ROC for a GW of 66 tons. Is that realistic?? 

Before I get into a tedious series of pitch/power experiments, did anyone check it thus far?

Also, and this is something subjective that I can't back up with figures, but the FBW feels a bit "unstable". Removing the pressure from the stick will cause make the plane bounce back a little as if it needed a little bit of trim.

 

anyone with any input on this?

Ok, Ok, since I am a performance guru, give me the airport and altimeter used for your 66 ton aircraft. I will tell you what the real world aircraft will do by running charts.

Rick

[G550flyer 1,013]

32 minutes ago, G550flyer said:

Ok, Ok, since I am a performance guru, give me the airport and altimeter used for your 66 ton aircraft. I will tell you what the real world aircraft will do by running charts.

Rick

Wait, I knew I had done this before at some point. I had to check my posts and I found the test I did for the FBW A320. You can use the same numbers for a comparison.

 

Ok, I took a look and here is what I have found.

This data will be based on a old non NEO A320 with the CFM engines.

At 76kg at standard day conditions, it takes an A320 to go from brake release to 1500ft 2 minutes. It will take that same aircraft to go from brake release to 5000ft 3 minutes. If you average this and do the subtraction, you are looking at about 3500ft per minute to go from 1500 to 5000ft. That falls in between your 3000 to 5000ft per minute. Now, we know at those altitudes there will be configuration and speed changes. To get a good comparison, lets compare your findings against this measurement. From brake release, we are looking at a 76kg aircraft taking 27 minutes and 175nm to climb up to FL350. Use standard day conditions at an airport at sea level. Don't flex and ensure to accel to 250kts passing 1500ft, 300kts passing 10000ft and maintain mach .78 once 300kts and .78 meets. Report back the take it takes to get to FL350. The FBW 320 tends to use 290 in the climb so hard select it to 300.

Rick 

Here is the original thread link.

 

Edited June 3, 2022 by G550flyer
add

[Donstim 109]

Hey Rick,

As a performance guru, you should know that using CEO performance for a NEO is not going to be valid. (I'm talking about your FBW A320NEO performance assessment.) It only takes 23 minutes and 148 NM for an A320NEO/Leap 1A-26 to climb to FL 350 starting at 76 T with a 250/300/0.78 speed schedule at ISA+10 C, 33% CG, A/C on normal, and A/I off. For an A320CEO with CFM56-5B4 engines, it takes 29 minutes and 192 NM for the same conditions.

[ha5mvo 253]

So I made some experiments.

At 60 Tons, 15 degrees, standard pressure and no wind.

Reaching  5000 ft at 4200 f/min (somewhat high) I got the following pitch/power settings:

57%-4.5 degrees - 230 knots 

53%-5 degrees - 210 knots

57% - 7 degrees about 15 knots below green dot (should be green dot)

at 10000 feet 

60% - 5 degrees - 210 knots

Certainly needs polishing but not way off either. 

What kept bugging me, is that I had to fight the controls until I could achieve a stable pitch. This is not something that should happen with a FBW. Albeit we are talking a series of minor corrections, the plane should not recoil once pressure has been removed off the stick. 

[Ilari Kousa 116]

11 hours ago, MattNischan said:

Very much so. Pretty much every aircraft dev will tell you that they will receive downright opposing suggestions from two different pilots all the time (who, generally don't at all have exact figures), and that often pilots "absorb" (for lack of a better term) a lot of flight model differences because they're used to, well, actually flying a plane, which is a much more feel and muscle memory sort of exercise than a test pilot type of situation where exact telemetry is also important.

Generally if the pilots are in a majority agreement you know you at least hit the feel enough so that it's in that muscle memory ballpark, but even still you can be off from book figures by a decent amount. Compounding that is that book figures are themselves not hugely precise: it's what a few planes did on average on a best-possible-average type day with humans at the stick. So often you have to really divine an alternate reality that compromises between all these different inputs.

On top of all that the million pound simulators are using table lookup physics which are derived from, you guessed it, the book figures, and they effectively have zero non-normal envelope data. So that adds another layer of inexactness. But it's good enough for training purposes (because again, good pilots "absorb" these differences, and the procedures are really what is being trained in these sims).

You do know that EOE modeling has been introduced in newer FFS devices?