The actual range of ajs37

[IDontLikeBigbrother]

I'm trying to test the max range of ajs37. Taking off from Novoroblabla airport, one of the most north west airport, gradually climbing up, flying to vaziani, reverse the direction and trying to fly as far as I can.

Pay load: only central fuel tank.

Altitude: 9000m

Speed: 0.87mach(economic speed at this altitude, manual page 173)

Never use afterburner, even during the take off.

 

 

When the fuel completely ran out:

the range at this point: 1900km( the plane glided about 100km after that)

So here is what I get: 1900km(with fuel tank), which is 200km shorter from the manual number(page 19)

Actually 1900km is the range when the fuel is completely dry: that means no reserved fuel for landing. If 10% fuel, a reasonable amount of fuel for landing is accounted in, the range should be around 1650km.

I think it is quite impossible to achieve the max range of 2100km, unless the plane is magically spawned in high altitude,perfectly keeps economic speed, makes no turn at all, and doesnt land at the end. That's the only way to reach the max range of 2100km.

Edited May 7, 2021 by IDontLikeBigbrother

[TLTeo]

Max range flight profiles are a specific altitude, with a specific climb profile though (otherwise e.g. the FPAS page on the Hornet wouldn't exist - one would just park it at some high-ish altitude, set a predetermined Mach number with ATC, and call it a day). There's no reason why the flight profile you followed should yield exactly the maximum possible range of the aircraft.

[renhanxue]

See this thread for some charts from the SFI (flight manual for the real aircraft):

The chart is for payloads in group 1 (drop tank and maybe a sidewinder, I don't remember off the top of my head). 2100 km seems optimistic and I don't know where the figure comes from. I suspect that for a truly optimized distance economical flight you'd probably want to start lower and climb gradually as fuel is expended though. That's just speculation on my part however.

 

Did you jettison the drop tank in the test flight by the way?

edit: ok, went and looked. group 1 payload is represented by drop tank, 2x rb 24 and the KA and KB countermeasure pods. SFI says you should be able to do almost 1600 km clean with 5% fuel reserved for taxi and 15% in reserve for landing, or maybe 1650 if I'm reading these charts right and you start climbing to 10km during the later half of the flight. 2100 km does sound rather optimistic to me but might possibly be achievable with the perfect flight profile and small margins.

Edited May 8, 2021 by renhanxue

[IDontLikeBigbrother]

Of course I jettison the tank after it's empty.

I checked the chart, maybe my problem is that the plane was too high. 9000m altitude is not on the chart at all. it seems that the best altitude is around 7000m.

[MYSE1234]

7 hours ago, IDontLikeBigbrother said:

Of course I jettison the tank after it's empty.

I checked the chart, maybe my problem is that the plane was too high. 9000m altitude is not on the chart at all. it seems that the best altitude is around 7000m.

In DCS best altitude is 5000m when you are using max dry, where it uses about 75% of the fuel at ground level. After 5000m it starts going back up, such that at 10000m you're back at ground level usage.
https://docs.google.com/spreadsheets/d/1pric8e_euS3N4TVDADTzb8p8I7G_6iL9FtZ9l6FGGRw/edit#gid=434619095

Edited May 9, 2021 by MYSE1234

[Machalot]

7 hours ago, MYSE1234 said:

In DCS best altitude is 5000m when you are using max dry, where it uses about 75% of the fuel at ground level. After 5000m it starts going back up, such that at 10000m you're back at ground level usage.
https://docs.google.com/spreadsheets/d/1pric8e_euS3N4TVDADTzb8p8I7G_6iL9FtZ9l6FGGRw/edit#gid=434619095

 

That is bizarre. If I understand it right they are modeling ultra-rich combustion at high altitude. Seems worthy of a bug report. 

[MYSE1234]

51 minutes ago, Machalot said:

That is bizarre. If I understand it right they are modeling ultra-rich combustion at high altitude. Seems worthy of a bug report. 

Already done quite some time ago. Apparently it's fixed..

Edited May 9, 2021 by MYSE1234

[Machalot]

2 hours ago, MYSE1234 said:

Already done quite some time ago. Apparently it's fixed..

 

I take it your use of "apparently" is sarcastic. 

[MYSE1234]

13 minutes ago, Machalot said:

I take it your use of "apparently" is sarcastic. 

Very much the case. 

[renhanxue]

On 5/9/2021 at 11:42 AM, MYSE1234 said:

In DCS best altitude is 5000m when you are using max dry, where it uses about 75% of the fuel at ground level. After 5000m it starts going back up, such that at 10000m you're back at ground level usage.
https://docs.google.com/spreadsheets/d/1pric8e_euS3N4TVDADTzb8p8I7G_6iL9FtZ9l6FGGRw/edit#gid=434619095

 

Amazing work! That's a suspicious discontinuity if I ever saw one...

Edited May 10, 2021 by renhanxue

[TLTeo]

@IronMike this may be worth looking at, there's no way fuel consumption should work that way

Edited May 10, 2021 by TLTeo

[IDontLikeBigbrother]

On 5/9/2021 at 4:35 PM, Machalot said:

I take it your use of "apparently" is sarcastic. 

That's a nice one!

[LazyBoot]

On 5/9/2021 at 11:42 AM, MYSE1234 said:

In DCS best altitude is 5000m when you are using max dry, where it uses about 75% of the fuel at ground level. After 5000m it starts going back up, such that at 10000m you're back at ground level usage.
https://docs.google.com/spreadsheets/d/1pric8e_euS3N4TVDADTzb8p8I7G_6iL9FtZ9l6FGGRw/edit#gid=434619095

 

Since HB seems to be more actively looking through this part of the forums I'll bump this and tag @IronMike

[IronMike]

Noted, thank you. Apologies for missing the first notification, didnt see that. We will investigate this - that is fuel flow. Great chart above, very helpful, thank you. 

As for max range: hard to say unless done under exact same conditions, but the fuel flow being off, as it seems, would explain why it is not within a closer margin. Definitely something we need to look in to.

Edited September 22, 2021 by IronMike