This A/C is Underpowered
Hi all,
Recently come back to this aircraft after not flying it in awhile. I have owned it for several years and have always felt this way: It doesn't have the power of it's real-life counterpart. I have dispatched this airplane in the real world and have rode up front several times, and this beast shoots off the runway like a rocket, even on RTOP takeoffs. But in the sim, you don't get that. I don't think it's my setup because I've installed it on a couple different machines, and FSX as well as P3D. I just took off from KJAC, a high-altitude airport with a short runway. My previous airline operated the Q400 into this airport without ever having weight restrictions, unless it was in the winter in icing conditions. Aurasim's takeoff numbers told me that at NTOP I would have 1300M of positive stopping margin, but I found myself rotating at the very end of the runway. This obviously isn't right. It's a shame because this is an otherwise-flawless product. Seeing as how I haven't seen this come up in the forums before, I assume I am in the minority in this thinking. But if the developers wouldn't mind taking a look, it would be appreciated.
Thanks,
Ben
Comments
Thank you for your input. At this stage in the game changes to performance parameters is not a high priority. We know that our product is not perfect, and like anything there can be room for improvement. I do agree that some of the performance calculations/operations for high elevation airports are not close to real world ops.
Being a dispatcher does provide one with a wealth of back ground knowledge regarding the performance specs and your required jump-seat observations certainly gives you a birds eye view of how the aircraft operates, especially in and out of special airports. However, having worked with several active type rated Q400 pilots at the beginning and though out our development stages we have developed the add-on as best as possible in order to facilitate the aircraft's complex functionality within the simulator platform. Of course one is always able to make tweaks, but doing so comes at a cost in that some other system(s) usually ends up being affected.
Slowing down development to reinvent the wheel is not an option at this point. However feel free to supply us with details regarding where we fall short, and if you have supporting data for reviewing purposes.
Cheers
Hello, I just have a misconception about the stop margin or do I mistranslate what I wrote. You write that you only rotate with NTOP at the end of the Rwy, but you talk about a stop margin. Stop Margin for me is the track I would still have if I had to drop out of the race after the complete stop. Can you please tell which airport, which Rwy, which TOW, which weather.
I tried to recreate that without knowing exactly what TOW and takeoff configuration you had in your attempt. I went to the structural MTOW without knowing to what extent this is even permissible at the airport with its 1920 meter Rwy. Likewise, I could only accept the start configuration and started with Flaps 15, bleeds off. The pictures show it, I got away well. Of course, I cannot say whether the Dash correctly reflects the original engine performance.
My data with live Weather:
MTOW 29570
Wind 029/04
Temp -3/-15
QNH 1019
Rwy 19
Hey guys,
Thanks for taking the time to respond, and going through the trouble of attempting to reenact my scenario. The other day, I was taking off around 60,000 lbs, so no where near MTOW, but at flaps 5 and a temp of around ISA + 15. I have come to the conclusion that Aurasim doesn't take into account elevation, so I have ditched it for this next exercise. I will refer to the spaghetti charts linked on this forum which I assume to be accurate.
Weather: winds calm, 22c (ISA + 20), altimeter 29.92. Flaps 15, bleeds off
The flaps 15 takeoff distance chart says the most weight I can take off a 6,300-ft runway is 59,750 lbs. This is about what would be required to take 68 passengers and bags to KDEN on a warm summer day. So that's what I will load up. With a proper accelerate/stop margin, I will assume to be able to rotate before the touchdown zone marker.
Well, I lifted off with around 750 feet of runway remaining. But when I replayed the scenario aborting at V1, you can see where my final resting place was. So, I would still argue that the plane is underpowered. Not by much, 5% or less. And I do realize this is a mature product and you don't have much of a motivation to tweak it at this point. But thanks for looking at it anyway.
Ben
Hi Ben,
I have the Q400 tables and at first sight I think you are too heavy for the Rwy lenght available. I'll post the results of my findings later on as I have a bit of work to do right now.
Regards,
JP
Remember also that your calculated takeoff data will include the use of an safety area beyond the runway for accelerate/stop distance calculations. Runway 19 has a safety area beyond the departure end 950ft long and 200ft wide, although it doesn't have an EMAS area to aid in deceleration. Hard to tell exactly from screen shits but looks right about where you came to a stop.
> Remember also that your calculated takeoff data will include the use of an safety area beyond the runway for accelerate/stop distance calculations. Runway 19 has a safety area beyond the departure end 950ft long and 200ft wide, although it doesn't have an EMAS area to aid in deceleration. Hard to tell exactly from screen shits but looks right about where you came to a stop.
Even if the runway does have a safety area in real life, the takeoff chart I used assumes a 6,300-ft runway.
And I am pretty sure safety areas cannot be considered usable for overruns for the sake of calculating takeoff numbers. Aborting takeoff and impacting approach lights, even if they are frangible, is not acceptable risk. A displaced threshold and I believe a blast pad can be used for calculations but not even EMAS IIRC.
And if you think my weight was calculated incorrectly please show me how. I used the spaghetti charts linked on this forum as that's the only source of reliable data I have at this point.
Ben
>
> Even if the runway does have a safety area in real life, the takeoff chart I used assumes a 6,300-ft runway.
>
> And I am pretty sure safety areas cannot be considered usable for overruns for the sake of calculating takeoff numbers. Aborting takeoff and impacting approach lights, even if they are frangible, is not acceptable risk. A displaced threshold and I believe a blast pad can be used for calculations but not even EMAS IIRC.
>
> And if you think my weight was calculated incorrectly please show me how. I used the spaghetti charts linked on this forum as that's the only source of reliable data I have at this point.
>
> Ben
Per FAA AC 150/5300-13, “STOPWAY STANDARDS. A stopway is an area beyond the takeoff runway, centered on the extended runway centerline, and designated by the airport owner for use in decelerating an airplane during an aborted takeoff”.
They are, in essence, imaginary lengthening of a runway to allow for higher weight takeoffs by allowing a plane to rotate closer to the departure end while still maintaining adequate stopping room and obstacle clearance in case of an engine failure at V1.
I looked at the KJAC charts in Jeppesen and It clearly designates a 950’ stopway.
Are your charts based on runway distance or accelerate/stop distance? If your goal is to do an abort at V1 and remain on the runway you need to find the accelerate/stop charts and reduce your takeoff weight as appropriate. However, as long as your accelerate/stop distance is less than 7250’ (6300’ runway plus 950’ stopway) you’re legal to depart even though you couldn’t remain on the runway if you aborted at V1.
The Jepp 10-9A page states that there is a 950' safety area, not stopway. You are correct that a stopway may be used in ASDA calculations, but not a safety aea. A runway safety area (RSA) or runway end safety area (RESA) is defined as "the surface surrounding the runway prepared or suitable for reducing the risk of damage to airplanes in the event of an undershoot, overshoot, or excursion from the runway." A RSA is a 'last line of defense,' if you will, and it is assumed that an aircraft incident beyond the scope of a standard abort has occured. Part of Part139 airport certification is having a level area immediately surrounding the runway and to make all objects in the safety area, such as localizer antennae, and approach lights frangible so that they can brake away upon aircraft impact. You would never have approach lights in a stopway such as at KJAC.
If you refer to the chart supplement for KJAC, the ASDA is in fact 6,300'.
https://aeronav.faa.gov/afd/26mar2020/nw_249_26MAR2020.pdf
Ben
Hi Ben,
I am not sure that the safety area should be taken into account in case of aborting take-off and, as stated on Jeppesen charts, is for "overrun incidents" and in case of too long landings it says: "... sometimes fail to stop on the runway and are at risk for a runway excursion".
We know that KJAC is 6451 Ft above sea level, the Rwy usable 6300 Ft, temperature taken for the calculations: OAT +22°C / ISA +20°C, wind calm, standard pressure QNH 1013 Hpa (29.92"), flaps 15°, Bleeds OFF.
There are few tables for the calculations, starting with the WAT limit but we are going to concentrate only on one graphic: Takeoff distance flaps 15°.
My calculations are very similar than your findings, the MTOW about 27 000 Kg (58 800 Lbs). This would give V1/Vr 114 Kts.
I did quite a few tests aborting the Toff run just below V1 and I get the same result ending after the runway end.
To stop before the runway end you need to have a MTOW of about 24 000 Kg (53 500 Lbs).
There is an airport that I use to fly a lot: VQPR, Alt 7352 Ft, Rwy 2105 m (6900 Ft) and using these tables it was perfect all the time, accelerate stop finishes just at the end of the Rwy.
May be I have a silly idea: is the lenght of the runway correct in FSX/P3D?
Regards,
JP
If I am not mistaken, there are not much differences if we consider the field lenght, the acc/stop and the TOFF Dist:
Unfortunately I cannot enclose the TOFF Distance graph due to the size but it shows 58 800 Lbs.
JP
I mean no disrespect to the developers and I have found a new love for this aircraft after discovering it is compatible with v5. It's amazing an aircraft released 7-8 years ago has stood the test of time. But one of the hallmarks of this airplane is the performance so I wish that were felt in the sim.
I have found where to make the necessary edits in the relevant XML files but I'm not sure if that would be breaking EULA. I realize this may have unintended consequences, and that the developers used highly advanced techniques to get this aircraft to fly by the numbers, but I think even just increasing the max thrust by 3-5% would do wonders.
Even at altitude, in the real thing at FL250/props 850 you still have to eventually pull the throttle back to avoid an overspeed. In the sim you are lucky to get it to 240 indicated at that altitude.
Ben
I found that as well:
PAVED 950X200 FEET SAFETY AREA AT THE DEPARTURE END OF RUNWAY 19. NOT USABLE FOR PERFORMANCE CALCULATIONS. ASPHALT POROUS FRICTION COURSE, PLOWED AND BROOMED DURING WINTER
However, looking at the aerial photograph, it looks usable:
https://www.google.fr/maps/search/kjac/@43.5982349,-110.7431531,461m/data=!3m1!1e3?hl=fr
I wanted to print out the performance charts at work today, I forgot. Therefore, only with enlargement on the PC (slightly out of focus) I calculated the whole thing for the 22 ° C, 59750 Ibs (27102 Kg), wind calm, Flaps 15, Rwy 19 mentioned here. In certain circumstances, i'm optically 20 meters 2 kts next to it, because of the blurriness in the picture. I use the same graphics as jpgmultimodal
I get a V1 of 112 Kts, a Vr of 116 Kts.
The TODA is 1875 meters (corrected by the slope 1940 meters), the TORA is 1660 meters (corrected by the slope 1780 meters. The acceleration-stop distance is 1820 meters (corrected by the slope 1860 meters).
I readjusted the whole thing again and came to a stop about 60 meters before the end of the Rwy. When I look at myself that my calculated value for the Accelerate-Stop distance is 1860 meters, which Rwy has 6300 meters, I'm not that bad.
Interesting that you were able to come to a stop, Frapre. I do see that you have a 5 knot headwind that wasn't supposed to be there, the temp is a few degrees less, and your V1 is 112 instead of the 116 I used.
Just to make sure nothing fishy is going on, I ran it again, this time using default scenery, and with weight in KG to make sure nothing weird is going on with the units conversion. Same result as before. I even tried an abort at 112 knots instead of 116, and went right off the end again; it wasn't even close.
The developers have admitted there are some issues with high density altitude, and I think that is what we are seeing here.
Ben
I did not notice the 5 Kts, had set the weather manually and actually set 0 Kts wind.
May I ask how you practice the takeoff, as a rolling or static takeoff? And the start abort, with max reverse and full braking action?
With regard to V1 and Vr, I had taken the values that I hopefully calculated correctly for me.
I applied full power and simultaneously released the brakes. And on the abort, I immediately applied max toe brakes and full reverse. But when V1 occurs with less than 1,000 feet remaining, there isn't much you can do.
Ben
I wait in the stand with the brakes applied until the full starting power is at hand, it always needs something, if you then roll naturally, valuable meters are lost. The brakes of the Dash do not hold them completely when you set the starting power.
Overall, however, it is a borderline matter here, and not all points are taken into account in the information available for the calculation of the start data. Aurasim also offers very little adjustment. If, as you said, you had to do it professionally, maybe you still know pilots from the old days, let them calculate the takeoff performance data correctly, we would be interested.
I seem to remember from Aerodata, when performance required a static takeoff, it would specify in the data returned. But they were extremely rare, and you are talking maybe a 50-foot difference, when I was over 500 feet into the overrun safety area. And I don't know any Q pilots anymore; in fact, the airplanes we flew at my previous airline went to an operator across the pond who is now recently defunct.
Ben
Hi Ben,
You said: " If the chart says an area of pavement isn't usable, it isn't usable". The chart says: "NOT USABLE FOR PERFORMANCE CALCULATIONS. It is not exactly the same. You should only take the 6300 Ft for the calculations and ignore the 950 Ft Safety area.
The calculations with the graphs are correct as far as I know. I never flew the Q400 but I used to work with similar charts for other aircrafts when we had restrictive runways.
I remember an airport where I used to fly a lot: EGJJ where there was a stopway at the end of Rwy 27 (26 now). It was made with gravel and was in case of you could not stop on the Rwy as there is a cliff at the end. If you end up there, the acft could be damaged but it was better than to fall over the cliff. The gravel is not there anymore.
It could be something similar with KJAC.
Another thing to bear in mind, the calculations are made without using the reverse. Of course, on a short runway with a failure just before reaching V1 you would use the reverse if it is available.
It is very rare, except in training, to have to abort 1 Kt before V1but the calculations are made this way and, most probably, these extra 950 Ft are there to stop you if needed.
You are absolutely right about FSX/P3D saying that high altitudes could be a problem, same with temperature, we do not know how accurate it is when we enter these parameters in the sim. Something else which I find a bit weak are the brakes, not only for the Q400 but for every plane. We cannot do a thing about it. Well this sim cost only few $/€/£ and it is quite good for that kind of money.
One last thing, I had a look at ORBX KJAC and could not find if this 950 Ft area has been designed.
Interesting article on this subject here:
https://aviationtechno.com/general-principles-take-off/
Regards,
JP
Ben
So in a nutshell from the MJC side of things, modeling of the Q400 performance was/is an extremely complex task due to its unique propeller design, and it's possible that at some given weight, temperature, pressure, wind, runway condition or altitude it will not match the real aircraft performance charts or Aerodata, which by the way is very restrictive in many cases at special airports in relation to what the aircraft's performance is capable of. The Q400 in of itself is a beast has performance characteristics that surpass any turboprop in its category, the smaller variants of the DeHavilland family I have over 30 years experience with and I know Aerodata hampered our operating performance drastically. Much of it having to do with loosing an engine for the given departure.
@Whoashloppy
We do not recommend that you manipulate the configuration files as they are fine tuned to provide the closest realistic performance under "most" situations. Altering parameters will/can result in reduced, erratic or unrealistic behavior if conditions change.
Cheers
> Great discussion gents, lots of input.
>
> So in a nutshell from the MJC side of things, modeling of the Q400 performance was/is an extremely complex task due to its unique propeller design, and it's possible that at some given weight, temperature, pressure, wind, runway condition or altitude it will not match the real aircraft performance charts or Aerodata, which by the way is very restrictive in many cases at special airports in relation to what the aircraft's performance is capable of. The Q400 in of itself is a beast has performance characteristics that surpass any turboprop in its category, the smaller variants of the DeHavilland family I have over 30 years experience with and I know Aerodata hampered our operating performance drastically. Much of it having to do with loosing an engine for the given departure.
>
> @Whoashloppy
> We do not recommend that you manipulate the configuration files as they are fine tuned to provide the closest realistic performance under "most" situations. Altering parameters will/can result in reduced, erratic or unrealistic behavior if conditions change.
>
>
> Cheers
Agree on Aerodata being super restrictive with the Q. Introduce deicing fluids and all of a sudden you are kicking 20 passengers sometimes. Or having to find DD alternates when we all know the Q can clear the Rockies on one engine.
Ben