Fuel Flow/Burn
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What do the profile options mean?
LIke... High Speed I assume is is maximum Thrust (using VS or IAS mode)? Long Range I guess is a lower power climb (ie 500-1000fpm). For descent I guess High Speed it essentially just an idle throttle high FPM descent over a shorter distance while Long Range is just that, idle or near idle descent over a much larger distance than the High Speed one?
For Cruise profiles, M70 is just maintain Mach .70 I guess, not to hard to work out. MCR is setting the TMS to Max Cruise Thrust, and just flooring it and riding the barber pole? LRC is low power cruise for max distance, like I'm guess .5 Mach or something?
Would be nice to get more information on what these meant, haha.
I haven't really had the issue with maintaining speed like some folks here have mentioned. It can be a little fiddly at the start with initial cruise, but after that its generally fine, usually letting me wander away or watch some Youtube while flying along.
@melon said in Fuel Flow/Burn:
What do the profile options mean?
I found this in a Mahan Air SOP for the BAE146/RJ
4. CLIMB Three climb techniques are recommended: 4.1.1 High Speed Climb (HSC): 280 IAS or 0.60 IMN. Coincident at approximately FL 190. 4.1.2 Long Range Climb (LRC): 250 IAS or 0.60 IMN, coincident at approximately FL 240. 4.1.3 Steep Gradient Climb: 220 KTS (146‐300).This technique can be used to reach a level or altitude by a particular point. For absolute max gradient performance, climb at VER (VFTO +10). Set climb thrust as soon as convenient (observe maximum 5 minutes) after flaps retraction, or at the thrust reduction altitude for the noise abatement procedure. [...] 6.5 DESCENT SPEED SCHEDULE: Two descent profiles are published: 1‐ Long Range 0.6M/250 kt 2‐ High Speed 0.7M/290 kt In practice, any combination of speeds can be used but ATC may require high forward speed to help fit the relatively slow BAe146 into the arrival flow with other, faster jets. For this reason the high speed profile is favored by many operators. Remember, to observe speed limit points and the limitation of 250 kts below 10 000 ft.As for TGT setting, the same SOP has
The normal power climb setting is 840 ºC TGT, although lower TGT may be used to conserve engine life if high climb performance is not required , (i.e.820 ºC) . -
@melon said in Fuel Flow/Burn:
What do the profile options mean?
I found this in a Mahan Air SOP for the BAE146/RJ
4. CLIMB Three climb techniques are recommended: 4.1.1 High Speed Climb (HSC): 280 IAS or 0.60 IMN. Coincident at approximately FL 190. 4.1.2 Long Range Climb (LRC): 250 IAS or 0.60 IMN, coincident at approximately FL 240. 4.1.3 Steep Gradient Climb: 220 KTS (146‐300).This technique can be used to reach a level or altitude by a particular point. For absolute max gradient performance, climb at VER (VFTO +10). Set climb thrust as soon as convenient (observe maximum 5 minutes) after flaps retraction, or at the thrust reduction altitude for the noise abatement procedure. [...] 6.5 DESCENT SPEED SCHEDULE: Two descent profiles are published: 1‐ Long Range 0.6M/250 kt 2‐ High Speed 0.7M/290 kt In practice, any combination of speeds can be used but ATC may require high forward speed to help fit the relatively slow BAe146 into the arrival flow with other, faster jets. For this reason the high speed profile is favored by many operators. Remember, to observe speed limit points and the limitation of 250 kts below 10 000 ft.As for TGT setting, the same SOP has
The normal power climb setting is 840 ºC TGT, although lower TGT may be used to conserve engine life if high climb performance is not required , (i.e.820 ºC) . -
What does the "co-incident at FLxx" mean? Do you set that speed at FLxx and climb, or do you climb at that speed until FLxx?
Thx
@b3lt3r They mean that 250 KIAS will equal Mach 0.6 at approximately FL240 etc. So if you were climbing at 250 KIAS then you could switch from IAS to MACH hold mode passing through approximatively FL240, and vice versa on the descent.
Martyn - Development Manager
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@b3lt3r They mean that 250 KIAS will equal Mach 0.6 at approximately FL240 etc. So if you were climbing at 250 KIAS then you could switch from IAS to MACH hold mode passing through approximatively FL240, and vice versa on the descent.
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@melon said in Fuel Flow/Burn:
@johan217 Oh that is really interesting, where does one acquire these sorts SOPs?
Some of these are floating around the interweb. I got this one from scribd (requires subscription, so I don't think I can share the full pdf here, sorry).
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Apologies for the thread resurrection but this appears to closely relate to the issue I am seeing.
In the latest version in MSFS2024, I am seeing fuel burn numbers in the simulator approximately 50% lower than the Simbrief estimates. I am using the Just Flight 146 Simbrief profiles and I believe they are accurate, I believe the issue is on the MSFS side.
Is anybody else experiencing this? Is it potentially a regression of an earlier fix, either with the product or MSFS2024 itself?
I am using Kgs as the units, in case this has any bearing.
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We aren't aware of any discrepancies between the fuel burn predicted by Simbrief and the actual fuel burn in the simulator, and those have both remained constant for some time now. Note, we do recommend using the custom 146 Simbrief profiles with the Just Flight (MSFS) prefix: https://support.justflight.com/en/support/solutions/articles/17000140885-146-professional-msfs-simbrief-profiles
If you have any examples of Simbrief OFPs that show inaccurate fuel burn vs. the simulator, could I kindly ask you to open a ticket with Just Flight Support via the following link and include those examples: https://www.justflight.com/support
Our support team will then be able to investigate further.
Mark - Just Flight
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Just want to back up what @Cal is saying, and the issue is not really a wrong simbrief profile, but simply that the fuel flow is way lower than any real world data.
Typically you would expect up around ~2000 kg/hr in cruise according to various sources (would also be nice if the JF manual included burn data), but even in worst case conditions and pushing it right to the barber pole you will burn much less in the sim. Think i typically ended up closer to 1200 kg/hr in high speed cruise.
I was gathering data to write a post about it myself, but real life intervened, and now I haven't flown the 146 for a while. -
Thank you both @Mark and @Avionic for your replies.
I can confirm I am using the custom 146 Simbrief profile, though as has been mentioned, the problem is unlikely to be with the profiles but more likely with the actual fuel burn rates in the simulator.
Using my latest 146 flight as an example, the estimated Enroute Burn was 3930kg for a Route Distance of 614 nm (Estimated TOW 40,671 kg). The actual recorded burn was 2637kg.
I am happy to provide further flight plans, figures etc and raise a support ticket with those details but I get the impression there is something more fundamental going on here. Simulator settings? Other possible conflicting addons such as GSX? Etc.
Thank you both again.
