[WIP] Pylon and Stores Drag

[greenmamba]

This is a question to anyone ,

 

Don’t you have the feeling that the fuel tanks have a too high of drag coefficient ? The hornet is a WIP but I really feel like having to wing tanks adds too much drag.

[Deano87]

You may have been spoiled by other jets that have big engines and plenty of wing like the F-15. The Hornet was never really blessed with a turn of speed, specially when weighed down with tanks etc.

 

Apart from your gut feeling that it’s too draggy do you have any data to support your feeling? There might be something in the Natops manual about drag penalty for tanks and reasonable cruise power/speeds etc. I dunno <shrug>

[donkeyrider]

I remember Jello mentioning in one of his podcasts that the legacy Hornet is quite draggy with 2 fuel tanks - he was comparing it to the Super Hornet.

[greenmamba]

You may have been spoiled by other jets that have big engines and plenty of wing like the F-15. The Hornet was never really blessed with a turn of speed, specially when weighed down with tanks etc.

 

Apart from your gut feeling that it’s too draggy do you have any data to support your feeling? There might be something in the Natops manual about drag penalty for tanks and reasonable cruise power/speeds etc. I dunno <shrug>

 

No no i just have my gut feeling, i have no data. But i will get used to the fact that the Hornet gets very draggy with the two wing tanks. I have the F-15 module but never flew it ..... i just flew other sims before that.

 

But i slowly get the feel for the Hornet, i find that anytime i need a bit of speed i either pitch down 5 degrees in the turn or i just unload the plane to 0 G´s or a little AB kick.

[greenmamba]

I remember Jello mentioning in one of his podcasts that the legacy Hornet is quite draggy with 2 fuel tanks - he was comparing it to the Super Hornet.

 

Ah oki, well then i just need to get used to it.

[Tenkom]

[WIP] Pylon and Stores Drag

 

I want to discuss the drag amount on the launchers for the A-A missiles on the Hornet. Specifically the ones for the aim-120s. I recorded a short video showing the numbers I found:

 

TL;DW:

It is a simple straight and level full AB speed test with 2(3) different configurations,

Single aim-120c with launchers on inner wing pylons

Just the launchers

And wing tanks.

Speed clean: 822 kts

Speed with missiles and launchers: 694 kts

Speed with only launchers: 730kts

Speed with wing tanks:726kts

 

So the wing tanks are only SLIGHTLY more draggy than just those tiny launchers?

This seems very unrealistic to me.

 

It also makes it very painful to fly around with missiles since the plane becomes so slow.

 

I haven't seen anybody mention this and if it really is wrong(and it's not just me being crazy) then it must be a really simple fix.

[Eldur]

I noticed this right away when the Hornet was new and I mentioned this several times and IIRC someone did a similar test back then, but it hasn't been acklowledged. Those racks look pretty sleek and many have the impression that their drag is way too much. In general, many racks seem to be quite off. Try carrying 8 Mk 83 and 2 Mk 82 for example and do the same test with those, you will be amazed. If you want to see more, repeat with those 6x BDU-33 racks

 

On a side note, even some stores seem to be way off as well. Load up max LAU-61s and see how the Hornet converts into an A-10 with afterburners performance-wise. Don't forget to take a peek at the checklist page there

[Eddie]

Drag index for a LAU-115 with 2 LAU-127 is 8.8. With two AIM-120s on the launchers it’s 18.8. Drag index for a single 330 Gal tank on the wing is 14.5. So yes, two AIM-120s is quite draggy, as are the clean launchers. An AIM-120 on the fuselage stations only has a DI of 4.

 

The DI for a single LAU-61 is 31.5, before you account for the BRU-33s, shouldn’t be surprising that 8 of them slows the jet down so much really should it?!

Edited December 1, 2018 by Eddie

[Wags]

Pylon drag is WIP.

[Uberick]

Huh, thats interesting. Can we jettison the launchers yet? I remember trying a while back and it didn’t work?

[Tenkom]

Drag index for a LAU-115 with 2 LAU-127 is 8.8. With two AIM-120s on the launchers it’s 18.8. Drag index for a single 330 Gal tank on the wing is 14.5. So yes, two AIM-120s is quite draggy, as are the clean launchers. An AIM-120 on the fuselage stations only has a DI of 4.

 

The DI for a single LAU-61 is 31.5, before you account for the BRU-33s, shouldn’t be surprising that 8 of them slows the jet down so much really should it?!

 

Where do you get these numbers?

[Eddie]

The F18AC-NFM-200.

[Eldur]

Drag index for a LAU-115 with 2 LAU-127 is 8.8. With two AIM-120s on the launchers it’s 18.8. Drag index for a single 330 Gal tank on the wing is 14.5. So yes, two AIM-120s is quite draggy, as are the clean launchers. An AIM-120 on the fuselage stations only has a DI of 4.

 

The DI for a single LAU-61 is 31.5, before you account for the BRU-33s, shouldn’t be surprising that 8 of them slows the jet down so much really should it?!

 

Great to have some numbers, seems reasonable.

 

In case of the LAU-61 there's one thing though: Where are the caps? We have them on the Harrier and F-5E. Are they not being used on the Hornet? (Would ask the same for Zunis) This should reduce the drag quite much. In case of those launchers though a lot of the performance loss also comes from it's sheer overweight. Getting the Hornet up to like 70k lbs is quite easy with those pods in DCS at the moment which is very far from being realistic.

 

Pylon drag is WIP.

 

Thanks for confirming, was kinda expected

[Frederf]

Clean DI vs 330 gallon on 3/7 is 0 versus 29.

 

With 400 engine (DCS 404) Vmax at MIL at 20,000' 34klb is

Clean M0.975

DI 25 M0.960

DI 50 M0.948

Estimated with DI 29, M0.959.

 

That's 599 KTAS clean and 589 KTAS DI 29. OK now you can go check at that weight and altitude is your top MIL speed 10 KTAS slower with the two wing tanks or not?

[Fropa]

Pylon drag is WIP.

This is good to know. Thanks, Wags! :)

[WildBillKelsoe]

Drag index for a LAU-115 with 2 LAU-127 is 8.8. With two AIM-120s on the launchers it’s 18.8. Drag index for a single 330 Gal tank on the wing is 14.5. So yes, two AIM-120s is quite draggy, as are the clean launchers. An AIM-120 on the fuselage stations only has a DI of 4.

 

The DI for a single LAU-61 is 31.5, before you account for the BRU-33s, shouldn’t be surprising that 8 of them slows the jet down so much really should it?!

 

How did you get these calculations? Can you show how it is calculated?

 

Nevermind

Edited October 29, 2019 by WildBillKelsoe
source mentioned

[GumidekCZ]

Im not a programmer, but if all these available, should it take so long to fix the drag of all pylons, adapter, weapons?

Yeasterday I just use script scanner to search whole DCS about any script mentioning LAU-115C adapter and its drag. Found nothing. Its a mistery how ED scripted drags for all these.

FA-18C sample drag index calculation:

 

 

same can be found for FA-18E/F sample drag index calculation:

Missiles:

 

 

Adapters:

 

 

store drag interference:

These can be found for any weapon/adapter for Hornet (doc for C version not all interfrence data filled, but for E/F version..all is there).

 

When DCS F18C Hornet almost clean configuration, it can be fast as it should be according to this chart:

But when anything carried under wings.. its like to fly with aerobrake out. No wonder that other DCS jets can outperform Hornet so easily.

Edited April 19, 2020 by GumidekCZ

[Airhunter]

This is ED, they probably forgot about it. Pylon drag is one of many basic features that are fairly simple to fix/implement that are still missing.

[G B]

Im not a programmer, but if all these available, should it take so long to fix the drag of all pylons, adapter, weapons?

Yeasterday I just use script scanner to search whole DCS about any script mentioning LAU-115C adapter and its drag. Found nothing. Its a mistery how ED scripted drags for all these.

FA-18C sample drag index calculation:

 

[ATTACH]233106[/ATTACH]

 

same can be found for FA-18E/F sample drag index calculation:

[ATTACH]233107[/ATTACH]

Missiles:

[ATTACH]233108[/ATTACH]

 

 

Adapters:

[ATTACH]233109[/ATTACH]

 

 

store drag interference:

[ATTACH]233110[/ATTACH]

These can be found for any weapon/adapter for Hornet (doc for C version not all interfrence data filled, but for E/F version..all is there).

 

When DCS F18C Hornet almost clean configuration, it can be fast as it should be according to this chart:

[ATTACH]233111[/ATTACH]

But when anything carried under wings.. its like to fly with aerobrake out. No wonder that other DCS jets can outperform Hornet so easily.

 

The E/F pylons’ drag is in a completely different league than the legacy hornet’s. Interpolation wouldn’t work. Apples to oranges.

[GumidekCZ]

The E/F pylons’ drag is in a completely different league than the legacy hornet’s. Interpolation wouldn’t work. Apples to oranges.

How do you know? Are you Hornet pilot? or Boeing employee?

Even small kid playing with plastic models knows that C and E/F have different dimensions between pylons (E/F has less space between = more interference drag), but can be good data when compared with C version.

Edited April 19, 2020 by GumidekCZ

[gekoiq]

How do you know? Are you Hornet pilot? or Boeing employee?

Even small kid playing with plastic models knows that C and E/F have different dimensions between pylons, but can be good data when compared with C version.

 

As it turns out he *is* a Hornet pilot...

[G B]

As it turns out he *is* a Hornet pilot...

 

And Rhino :).

[G B]

How do you know? Are you Hornet pilot? or Boeing employee?

Even small kid playing with plastic models knows that C and E/F have different dimensions between pylons (E/F has less space between = more interference drag), but can be good data when compared with C version.

 

Not just the size. The geometry too.

[oldcrusty]

Not just the size. The geometry too.

 

I vaguely remember from the SB sim there was some sort of issue with inboard pylons, the angle or something, related to weapon separation characteristics?

Another difference between Hornets and Rhinos is the wing shape also. More pronounced "twist" on Hornet's outboard part of the wing?

[G B]

I vaguely remember from the SB sim there was some sort of issue with inboard pylons, the angle or something, related to weapon separation characteristics?

Another difference between Hornets and Rhinos is the wing shape also. More pronounced "twist" on Hornet's outboard part of the wing?

 

The pylons are canted. The inboard ones are the worst. They were initially straight during the design phase, but during testing they calculated there would be weapons separation issues, and the “fix” was to cant the pylons. As it turns out, it was a miscalculation and it was a nonissue, but by the time they realized it, the damage was done and the canted pylons were here to stay. It’s very unfortunate.

 

Do a Google Image Search for Super Hornet Pylons.