Sign in to follow this  
Nick M

Q400 to the stars! (FL600+)

Recommended Posts

Hi All,

 

Let me start by saying how much I love the Majestic Dash 8. The combination of fidelity, performance and the challenging short-haul sectors flown by the real thing makes it the best airliner sim for FSX in my book. My thanks go to all those involved in its development. 

 

There's one area of the flight dynamics which does trouble me though, as I posted in the thread: 'Help with Q400'. However, I think this subject is a bit off-topic for that thread, hence the new one.

 

I've now had the opportunity to do some more testing: this time with a fully-loaded Q400. I've posted a series of screenshots below showing what I experienced. I'd like to emphasize now that I'm in no way a real-world pilot (let alone a Q400 driver) so I'd appreciate the input of other Q400 users on this issue.

 

Screenshot%202014-09-24%2011.34.11.png?d

Here's the weight and balance sheet for the test flight. Close to max take-off mass with a 29000kg aircraft (including 4000kg of fuel).

 

Screenshot%202014-09-24%2012.25.49.png?d

Here's confirmation of the aircraft weight and fuel quantity in the sim prior to engine start. Following take-off from EGTE I set the condition levers to 900rpm (MCL) and climbed at 200 kts using the IAS AFCS mode. Needless-to-say vertical speed and deck angles were pretty extreme during the first part of the climb. Lucky this was a test flight!

 

 

Screenshot%202014-09-24%2012.44.54.png?d

Here we are just over 15 mins after take-off passing FL250. By this point V/S has decayed to +600fpm so you could be forgiven for thinking she hasn't got much climb left in her. However, after this shot was taken, I reduced the commanded IAS to 180kts which allowed the rate of climb to increase to +800fpm.

 

Screenshot%202014-09-24%2012.57.10.png?d

12 minutes later we're climbing through FL300: still at 180kts and +800fpm.

 

Screenshot%202014-09-24%2013.16.06.png?d

A further 10 minutes into the flight sees us still climbing at +800fpm at 180kts: now we're passing through FL460! However, a few minutes later V/S does start to drop rather suddenly.

 

Screenshot%202014-09-24%2013.28.59.png?d

An hour into the flight, we're passing through FL522, and V/S has dropped to 'only' +300fpm but we're still climbing steadily. I've also reduced the IAS to 158kts (Vclmb for out T/O weight) where it'll stay for the rest of the climb. You may notice the engine rpm starting to creep away from the FADEC commanded setting of 900rpm at this point.

 

Screenshot%202014-09-24%2013.56.22.png?d

After another hour in the air*, we've finally reached what seem to be the absolute ceiling for the aircraft at this weight: FL636! (We've also burned about half of the fuel on board by now.) I could have traded a bit of airspeed for more altitude as I did in the previous test when I flew right up to stick-shaker activation. RPM is clearly over-speeding at this point. Wonder what would happen in the forthcoming pro version which I think has failures? (*I'll own up to using time compression for this bit, although I hadn't previously in the flight.)

 

Here's the final portion of the flight see through the FSX 'flight analysis tool'.

Screenshot%202014-09-24%2013.59.06.png?d

 

In posting this, I just wanted to provoke a bit of discussion about what's causing this odd ability to reach excessive altitudes in a flight model which otherwise seems so accurate. Any input from the developers would be very welcome, although I realise the Majestic forum is probably the best place to get this... (I know - I should register there!) 

 

All the best,

Nick

Share this post


Link to post
Share on other sites
Help AVSIM continue to serve you!
Please donate today!

Pretty interesting result.  If you could get that up to Mach 2.0 it would make a great replacement for Concorde !!!

Share this post


Link to post
Share on other sites

Pretty interesting result.  If you could get that up to Mach 2.0 it would make a great replacement for Concorde !!!

 

It's certainly a bit odd Mark. There was a topic started on the Majestic forums on the subject about 18 months ago, but it didn't seem to be noticed by the Majestic developers. (I'd post a link, but can't work out how to link to a specific topic on the Vanilla forum they use.)

 

Anyway, the topic poster also compared the Q400 to the 'new fuel efficient Concorde'!

 

In spite of this, I really do enjoy flying it. (Although I've been distracted by a certain little Cherokee recently!)

 

Cheers,

Nick

Share this post


Link to post
Share on other sites

Majestic have used a completely different flight dynamics engine outside of FSX to make the Q400 so this may be a side effect of that technology.  FSX does very strange stuff sometimes....as an example on Concorde you can fly at FL550 - FL600 and Mach 2.0 but have the fuel balance all wrong and the CG in the wrong place....it will still fly just fine.

Share this post


Link to post
Share on other sites

Yes - that sounds like a likely explanation. I  know very little about JSBsim which I believe is behind the Majestic FDE (except that it's 'successor of the LARCSIM built by NASA'), but I'm sure it involves all sort of complex integration into FSX.

 

I suppose the obvious answer to this issue is "don't try and fly the aircraft above the service ceiling of the real Q400" (which I believe is 25,000-27,000 feet depending on equipment).

 

However, I'd still be interested to know if many other Q400 flyers can replicate this behaviour, as some people describe struggling to reach FL250.

Share this post


Link to post
Share on other sites

Might be worth posting this over at the Majestic forum Nick, then we'll get a direct answer from the developer.

 

 

http://majesticsoftware.com/forums/

 

Would be interesting to see what they say.

 

I know one of the beta testers very well, I'll give him a shout.

Share this post


Link to post
Share on other sites

I know one of the beta testers very well, I'll give him a shout.

 

Thanks Martin.

 

I'll be dropping Majestic an email a bit later to apply for forum membership.

 

Cheers,

Nick

Share this post


Link to post
Share on other sites

Well worth joining the forum, nice people the developers and no nonsense over there.

Share this post


Link to post
Share on other sites

How do we know this behaviour is unrealistic? Perhaps a Q400 could reach those altitudes if the engines continued to function well in the thinner air and the cabin was de-pressurised! :P

 

Whilst this is a bug, I consider it a very minor one and I'd rather the Majestic team invest their time and resources elsewhere; I can't see anyone bothering to fly the Q400 significantly above the service ceiling other than curiosity. Providing it flies realistic up to the service ceiling, that should be enough for 99% of users.

Share this post


Link to post
Share on other sites

How do we know this behaviour is unrealistic? Perhaps a Q400 could reach those altitudes if the engines continued to function well in the thinner air and the cabin was de-pressurised!

 

That's a good question and one which I posed in this post. However, even with such powerful engines on the Q400, altitudes approaching 70,000 feet where the curvature of the earth and daytime stars are both visible seem a bit extreme.

 

Screenshot%202014-09-24%2020.14.04.png?d

This is another image from a test flight with a 22,000kg take of mass. For this one I flew up to stick-shaker activation at FL688.

 

Your point about "providing it flies realistic up to the service ceiling" is well taken. I'm just interested to see if this issue is one which affects all users, as some posters have said they struggle to reach FL250 (maybe these are P3D users?).

 

Cheers,

Nick

 

P.S. I admit it - I'm a frustrated test pilot!

Share this post


Link to post
Share on other sites

I'm just interested to see if this issue is one which affects all users, as some posters have said they struggle to reach FL250 (maybe these are P3D users?).

It shouldn't make any difference as JSBSim does all the flight dynamics and performance simulation, FSX/P3D just acts as graphics engine and provides some environmental variables (e.g. weather, terrain).

 

Users struggling to attain FL250 are likely trying to climb at an IAS or V/S that is too fast for their gross weight and SAT.

Share this post


Link to post
Share on other sites

No - I guess you're right. Perhaps iffy climb profiles would be responsible for simmers posting that they're 'struggling' to reach the service ceiling. As I've said, none of this detracts from my enjoyment of the Majestic Q400. I do think it's an interesting little quirk of the FDE, but I suppose I'd be happier if I felt it was truly reflecting the real aircraft's behaviour at the edge of the flight envelope. However, I know this is one area where desktop PC sims do often struggle. 

Share this post


Link to post
Share on other sites

ckyliu, I respectfully disagree that, if true, it's an issue of little importance because it's outside of a realistic flight envelope.  While no realistically conducted flight would ever take us higher than FL270, If the plane can continue climbing to 60,000 feet, then it  likely possibly means that it's performance climbing up into the FL270-ish altitudes is off, an altitude at which it does affect us during realistic use.   Maybe next time I fly the Majestic, I'll try this out myself; tbh I'm not on a Majestic kick right now, so I don't feel like loading it up for a flight.  But when I do get back to flying it, like what NickM is getting at, I would also be happier to know that the FDE isn't hopelessly incorrect up at a realistic cruise altitude.  He's climbing at 800 fpm through FL270, near max weight, so I'm sure somebody ought to be able to scrounge up some real numbers from a manual or somewhere

Share this post


Link to post
Share on other sites

ckyliu, I respectfully disagree that, if true, it's an issue of little importance because it's outside of a realistic flight envelope.  While no realistically conducted flight would ever take us higher than FL270, If the plane can continue climbing to 60,000 feet, then it likely means that it's performance climbing up into the FL270-ish altitudes is off, an altitude at which it does affect us during realistic use.   Maybe next time I fly the Majestic, I'll try this out myself; tbh I'm not on a Majestic kick right now, so I don't feel like loading it up for a flight.  But when I do get back to flying it, like what NickM is getting at, I would also be happier to know that the FDE isn't hopelessly incorrect up at a realistic cruise altitude. 

 

 

According to Brendan Hatch (United Q400) and the FlyBe Q400 FO (Josh?) from the Airline2Sim videos, the Majestic is on the money for the most part.

 

It certainly climbs as expected up to normal cruise levels. Not really a concern here IMHO. 

Share this post


Link to post
Share on other sites

Perhaps if NickM is interested in comparing the Majestic's performance to the real airplane, within the normal envelope  of FL270, I found this http://cf.alpa.org/internet/alp/1999/mayQ400.htm.  It's a very detailed test flight profile with very specific numbers provided.  Here is another article with some performance numbers as well http://theflyingengineer.com/aircraft/proud-to-fly-a-turboprop-q400-vs-atr72  After reading these two articles, and looking at NickM's first post, I agree with you GHarrel, that the realistic performance within the normal operating altitudes does not seem to be compromised by this strange ability to climb north of 60,000. 

Share this post


Link to post
Share on other sites

Perhaps if NickM is interested in comparing the Majestic's performance to the real airplane, within the normal envelope  of FL270, I found this http://cf.alpa.org/internet/alp/1999/mayQ400.htm.  It's a very detailed test flight profile with very specific numbers provided.  Here is another article with some performance numbers as well http://theflyingengineer.com/aircraft/proud-to-fly-a-turboprop-q400-vs-atr72  After reading these two articles, and looking at NickM's first post, I agree with you GHarrel, that the realistic performance within the normal operating altitudes does not seem to be compromised by this strange ability to climb north of 60,000. 

 

Thanks for links KG - I'd seen the second one but that first article is new and I'll be sure to read it properly later.

 

For what it's worth guys, I'm definitely not suggesting that the Q400 flight model is borked within its service ceiling - just that the odd high altitude behaviour is worthy of further discussion/investigation. As per my first paragraph in this thread, I love the Q400 to bits. I've spend most of my time in her hand-flying approaches and trying to pull off respectable landings, so this high altitude stuff is a bit irrelevant I know!

 

Cheers,

Nick

 

P.S. Incidentally, I tested out the absolute ceiling of the NGX earlier today and was just about able to get a lightly loaded aircraft above FL500. However, at this point the 'coffin corner' effect was quite convincing, with the aircraft barely controllable between the stall speed and VNE.

Screenshot%202014-09-25%2014.02.51.png?d

Share this post


Link to post
Share on other sites

Bear in mind one thing here .....

 

[i'm not saying this explains the entirety of this result here, but is certainly a factor] ....

 

...the reason that the Q400 is limited to a FL250 max ceiling is nothing to do with performance.   It is entirely a statutory limitation (both sides of the pond), because the aircraft has no emergency oxygen system.    There is no passenger oxygen supply in the Q400 that drops down in fancy little masks, in the event of depressurization, or any other catestrophic failure.

 

Thus the aircraft is limited to FL250, so that it is never more than 15,000' away from getting down to a safe 'unpressurized' altitude.

Look at the power to weight ratio of those powerful 5,000shp-a-side PWs, and bear in mind the fact that Q400 pilots often talk about how powerful the engines are, and that they're the best things about the aircraft.

So don't think that a Q400 should struggle to get past FL250 in a climb - not at all; a King Air can get to FL350! 

 

I am not saying a real Q400 should/would be able to make FL600 but that it should be borne in mind that the FL250 ceiling is not imposed by performance, but by legislation, on the oxygen point

 

 

REFERENCES:

 

From this article here:-

 

http://theflyingengineer.com/aircraft/proud-to-fly-a-turboprop-q400-vs-atr72/

 

.... "the Q400 can reach FL250 in 16-18 minutes"       You will not find many aircraft that reach a PERFORMANCE-based ceiling in 16 minutes.   

 

 

From this article here:-

 

http://www.flyertalk.com/forum/continental-onepass-pre-merger-closed-posting/790410-q400-aweful.html

 

"The Q400 does have oxygen masks"

Share this post


Link to post
Share on other sites

So don't think that a Q400 should struggle to get past FL250 in a climb - not at all; a King Air can get to FL350! 

 

I am not saying a real Q400 should/would be able to make FL600 but that it should be borne in mind that the FL250 ceiling is not imposed by performance, but by legislation, on the oxygen point.

 

Indeed! And I think even a type-rated Q400 pilot may find it difficult to assess how high an 'unconstrained' Q400 could climb if they were allowed to try it. (Though maybe I'm wrong on this - not sure how much the training takes in extreme situations, but I found this statement interesting in the Wikipedia Article on Pinnacle Airlines Flight 3701 which I referenced in another thread: "Pinnacle Airlines has restricted flights to a maximum of FL370. It has also changed its training program to include high altitude operations in ground school and simulator training. In addition, each crew is taken in the simulator up to FL410 and shown what the airplane did on the night Flight 3701 crashed.")

 

I suspect the question of the absolute ceiling of the real world Q400 is probably one for the designers of the real thing!

Share this post


Link to post
Share on other sites

...the reason that the Q400 is limited to a FL250 max ceiling is nothing to do with performance.   It is entirely a statutory limitation (both sides of the pond), because the aircraft has no emergency oxygen system.    There is no passenger oxygen supply in the Q400 that drops down in fancy little masks, in the event of depressurization.

 

I am not saying a real Q400 should/would be able to make FL600 but that it should be borne in mind that the FL250 ceiling is not imposed by performance, but by legislation, on the oxygen point

Passenger oxygen masks are an option on the Q400, and if fitted the service ceiling increases to FL270. However, you still made a good point about the ceiling not being performance based, I suspect the FL270 is down to differential pressure structural limitations.

Share this post


Link to post
Share on other sites

A bit of feedback from the Developers on this topic over at the Majestic forums. Although Oleksiy's reply makes me feel a bit like a naughty boy, I can quite understand where he's coming from!

 

Needless-to-say: my enjoyment of the Q400 is undiminished and it's an add-on I won't hesitate to recommend it.

 

Will have to see what the PRO edition offers when it's finally available (the shared cockpit feature doesn't particularly interest me) but I'm certainly looking forward to seeing Majestic's implementation of the HGS.

 

Cheers,

Nick

Share this post


Link to post
Share on other sites

I second that, looking forward to the HGS.

 

So essentially Majestic are saying they coded the flight dynamics to perform accurately within the normal certified altitude parameters. Not necessary at altitudes that are excessive.

 

Fair enough I say, I'm happy it performs well in the normal certified regime. No point in wasting time coding that far outside the envelope.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this