What is specificall about D-30F6 engine and Mig-31 inlet

Cold war, Korea, Vietnam, and Desert Storm - up to and including for example the A-10, F-15, Mirage 200, MiG-29, and F-18.
  • Author
  • Message
Offline

garrya

Forum Veteran

Forum Veteran

  • Posts: 901
  • Joined: 25 Dec 2015, 12:43

Unread post27 Dec 2015, 18:28

sferrin wrote:"Can you explain the term " massive afterburner"¿ as far as I know they are not the engine with highest thrust in after burner ( I think F-135 , F119 have far higher thrust )"

This is what "massive afterburner" means:
Image

F-16 , F-15 have big engine too
Image
Image
sferrin wrote:Also, not all engines are created equally. The Mig-25's engine for example only produces ~22,500lbs of thrust on the bench. But I guarantee you it produces more than an F100 at say Mach 2.5 and 70,000 feet. Look at the size of the Mig-25s intakes. Look at the size of the nozzles. The Mig-25 relies a lot more on inlet compression than the F-15 does. The J58, J93, and Tumansky R-15B-300 are all low-pressure engines that relied upon the inlets performing much of the compression at high speeds and altitudes.

So bigger intake and bigger nozzle equal more thrust at high altitude and speed ? Why is that ?
Offline

garrya

Forum Veteran

Forum Veteran

  • Posts: 901
  • Joined: 25 Dec 2015, 12:43

Unread post27 Dec 2015, 18:32

vilters wrote:All aircraft are build for a mission.
=> Interceptors are build to "get there fast". That's the mission.

F-15A was build as 'the all round superior dogfighter" => That is a different mission.

Russia is LARGE.
Mig-31 has to get there FAST and with RANGE to spare and shoot "at speed and at range". Turning is NOT in its book.

Interceptors are build that way.

Remember : The clean F-104 that zoom-barrel rolled around a SR-71 at 72.000 ft?

Each aircraft is build for the mission.

But what is the special features that allow mig-25 , mig-31 to achieve what F-15 , su-27 unable to
Offline

garrya

Forum Veteran

Forum Veteran

  • Posts: 901
  • Joined: 25 Dec 2015, 12:43

Unread post27 Dec 2015, 18:38

borg wrote:Other smaller details:
For such large jet as Mig-31, both the relativt small wings have thin airfoil for less drag. Meaning it cant turn very well but its not part of its designed requirement.
Other details, even the Vertical Stabz is quite thin, and fairly sweeped back angle. A stark kontrast to the F-15, Su-27 and F-22 vertical stabz.

And the cockpit glass..
You say the Mig--31 has a draggy airframe..??
Compaired cockpit section and what I mention above with other jets, then you'll find the Mig-31 quite sleek ;)

The whole cockpit section of Mig-31 looks like it belong on a orbital Rocket.
A stark contrast to the F-22 cockpit section, with its bathtub design and fragile bubble cockpit glass.

It look a lot more draggy than the mirages IV
Image
Image
If the requirements is only speed then why didn't the mig-25 , mig-31 have a delta wing with high sweep angle ?
Offline

borg

Banned

  • Posts: 471
  • Joined: 20 May 2015, 10:11

Unread post27 Dec 2015, 19:52

Looking at static thrust will not tell us much.
But when flying up at 50000ft the dynamic thrust looks different.
The wide diameter on D-30F6 fan stages helps out a great deal.
Lots of air in. Lots of compressed air out.

As i learned, there are several stages of AB settings. I can only guess the Mig-31 cruises a lot on minimum AB settings when going supersonic.
The Mig-31 is so big and heavy with fuel, it need full AB to take off and get up to its service altitude.

It does operate in subsonic speed as well, it will give it longer mission range.

Delta wings is not an option. They general bleed more energy, when you start turning.
For such high speed the wings you see on Mig-31 are the best suited one.
Offline

garrya

Forum Veteran

Forum Veteran

  • Posts: 901
  • Joined: 25 Dec 2015, 12:43

Unread post27 Dec 2015, 20:57

borg wrote:.
The wide diameter on D-30F6 fan stages helps out a great deal.
Lots of air in. Lots of compressed air out.

Shouldn't big engine and big intake will cause a lot of drag too ,?
And TEG did say that for high speed operations you move a small mass of air at high velocity , so why the need for big intake ?
borg wrote:Delta wings is not an option. They general bleed more energy, when you start turning.
For such high speed the wings you see on Mig-31 are the best suited one.

If Mig-31 wing is the most suited one for high speed and high altitude then why fast aircraft like SR-71 , XB-70 , arrow all have delta wing with very high sweep angle design ?
Image
Image
Offline

garrya

Forum Veteran

Forum Veteran

  • Posts: 901
  • Joined: 25 Dec 2015, 12:43

Unread post27 Dec 2015, 21:12

can someone translate or explain this graph
Image
Offline
User avatar

sferrin

Elite 5K

Elite 5K

  • Posts: 5600
  • Joined: 22 Jul 2005, 03:23

Unread post27 Dec 2015, 22:12

borg wrote:Delta wings is not an option. They general bleed more energy, when you start turning.
For such high speed the wings you see on Mig-31 are the best suited one.


So the Mirage 2000 can't turn? Interesting. :roll: Delta wings are certainly an option as both the Blackbird and XF-108 used them. It's not like either the Mig-25 or -31 are going to be pulling high Gs at 70,000 feet anyway.
"There I was. . ."
Offline

basher54321

Elite 2K

Elite 2K

  • Posts: 2073
  • Joined: 02 Feb 2014, 15:43

Unread post27 Dec 2015, 22:15

garrya wrote:If Mig-31 wing is the most suited one for high speed and high altitude then why fast aircraft like SR-71 , XB-70 , arrow all have delta wing with very high sweep angle design ?



The wing type is normally chosen because it is deemed best for requirements and budget at the time and is technically viable of course. The USSR was no stranger to delta wings (Su-9/MiG-21) - other configurations tested included a high sweep VG wing (Ye-155R) but were rejected (e.g. Heavier with no benefits).

Other designers went with a delta and they would each have their own reasons for preferring it over other configurations.

You cant estimate things like drag by looking at photos - they will normally just mislead you - same with engine nozzle diameter - get the actual dimensions don't just guess based on a photo.
Offline
User avatar

sferrin

Elite 5K

Elite 5K

  • Posts: 5600
  • Joined: 22 Jul 2005, 03:23

Unread post27 Dec 2015, 22:35

basher54321 wrote:You cant estimate things like drag by looking at photos - they will normally just mislead you - same with engine nozzle diameter - get the actual dimensions don't just guess based on a photo.


I don't think anybody suggested engine nozzle size is an indicator of speed. What it IS an indicator of is that things aren't black and white. Trying to compare an F100/F110 to an R-15/J58/J93 isn't going to get very far as they're designed for completely different environments. Consider the F110 has a max dia. for 46.5" and a bench value of ~29,00lbs, while the R-15 has max. dia. of 59.5" and a bench value of ~22,500lbs.

R-15.jpg


Obviously there is more to it than how much thrust an engine produces on the bench.
"There I was. . ."
Offline

borg

Banned

  • Posts: 471
  • Joined: 20 May 2015, 10:11

Unread post27 Dec 2015, 23:15

sferrin wrote:
borg wrote:Delta wings is not an option. They general bleed more energy, when you start turning.
For such high speed the wings you see on Mig-31 are the best suited one.


So the Mirage 2000 can't turn? Interesting. :roll: Delta wings are certainly an option as both the Blackbird and XF-108 used them. It's not like either the Mig-25 or -31 are going to be pulling high Gs at 70,000 feet anyway.


I didn't say Delta wings like EF and Rafale can't turn.. did i :shock:
In fact they turn very well.
But for such high speed jet, when you turn (yes you have to turn the jet at some point).
Regular wings works just fine for Mig-31.

I said Delta wings bleed more energy when you turn.
Especial on high Alpha turn.
See F-16 vs Mirage ;)

When the Mig-31 has depleted their armoury. You want to turn it around as fast as possible and return to base.
Yes its around 5G, but still, you turn the jet to the best of its ability.
right there, any delta wing would give it some con, instead of pro.
Offline

borg

Banned

  • Posts: 471
  • Joined: 20 May 2015, 10:11

Unread post28 Dec 2015, 00:07

A very nice dokumentary on development of Mig-31.
Its a "Wings of Russia" production i think..
Some of the best dokumentation series out there.
Its very fair and with very little propeganda.

Enjoy:
https://www.youtube.com/watch?v=KkaLeAErsSE
Offline
User avatar

sferrin

Elite 5K

Elite 5K

  • Posts: 5600
  • Joined: 22 Jul 2005, 03:23

Unread post28 Dec 2015, 00:25

borg wrote:
sferrin wrote:
borg wrote:Delta wings is not an option. They general bleed more energy, when you start turning.
For such high speed the wings you see on Mig-31 are the best suited one.


So the Mirage 2000 can't turn? Interesting. :roll: Delta wings are certainly an option as both the Blackbird and XF-108 used them. It's not like either the Mig-25 or -31 are going to be pulling high Gs at 70,000 feet anyway.


I didn't say Delta wings like EF and Rafale can't turn.. did i :shock:
In fact they turn very well.
But for such high speed jet, when you turn (yes you have to turn the jet at some point).
Regular wings works just fine for Mig-31.

I said Delta wings bleed more energy when you turn.
Especial on high Alpha turn.
See F-16 vs Mirage ;)

When the Mig-31 has depleted their armoury. You want to turn it around as fast as possible and return to base.
Yes its around 5G, but still, you turn the jet to the best of its ability.
right there, any delta wing would give it some con, instead of pro.


Yeah but if all they're doing is turning around to head to base they aren't going to yank on the stick so far that bleed off is even in the equation. If you're dogfighting that's one thing. Navigational turning is something else altogether. Nobody is going to be tooling along at Mach 2.8 and 70,000 feet and go, "welp, guess it's time to go back to base" and haul the stick back for a 7G turn.
"There I was. . ."
Offline

borg

Banned

  • Posts: 471
  • Joined: 20 May 2015, 10:11

Unread post28 Dec 2015, 01:54

sferrin wrote:
borg wrote:
sferrin wrote:
So the Mirage 2000 can't turn? Interesting. :roll: Delta wings are certainly an option as both the Blackbird and XF-108 used them. It's not like either the Mig-25 or -31 are going to be pulling high Gs at 70,000 feet anyway.


I didn't say Delta wings like EF and Rafale can't turn.. did i :shock:
In fact they turn very well.
But for such high speed jet, when you turn (yes you have to turn the jet at some point).
Regular wings works just fine for Mig-31.

I said Delta wings bleed more energy when you turn.
Especial on high Alpha turn.
See F-16 vs Mirage ;)

When the Mig-31 has depleted their armoury. You want to turn it around as fast as possible and return to base.
Yes its around 5G, but still, you turn the jet to the best of its ability.
right there, any delta wing would give it some con, instead of pro.


Yeah but if all they're doing is turning around to head to base they aren't going to yank on the stick so far that bleed off is even in the equation. If you're dogfighting that's one thing. Navigational turning is something else altogether. Nobody is going to be tooling along at Mach 2.8 and 70,000 feet and go, "welp, guess it's time to go back to base" and haul the stick back for a 7G turn.


Consider this:
When you fly towards enemy targets at mach 2+ and pluss the enemy might fly towards you, do i need to point out the distance between the two jets are closing fast..
So yes, you would want to turn around as quick as possible, even if its a Mig-31.
When your weapons are depleted, you head back to base, as fast as possible, there might be bandits on your six, so no time to hang about.
Offline
User avatar

sferrin

Elite 5K

Elite 5K

  • Posts: 5600
  • Joined: 22 Jul 2005, 03:23

Unread post28 Dec 2015, 03:42

borg wrote:Consider this:
When you fly towards enemy targets at mach 2+ and pluss the enemy might fly towards you, do i need to point out the distance between the two jets are closing fast..
So yes, you would want to turn around as quick as possible, even if its a Mig-31.
When your weapons are depleted, you head back to base, as fast as possible, there might be bandits on your six, so no time to hang about.


So you're going to base your whole design on a maybe? A delta is the best way to go when you plan on spending a lot of time at high speeds. That's why the Blackbirds had deltas, the Kingfish had one, the B-58, XF-108, XB-70, Avro Arrow, all the high speed Mirage designs, Concord, Tu-144, etc. etc. A delta isn't the ONLY way to do it it's just the best way.
"There I was. . ."
Offline

garrya

Forum Veteran

Forum Veteran

  • Posts: 901
  • Joined: 25 Dec 2015, 12:43

Unread post28 Dec 2015, 12:38

borg wrote:
Consider this:
When you fly towards enemy targets at mach 2+ and pluss the enemy might fly towards you, do i need to point out the distance between the two jets are closing fast..
So yes, you would want to turn around as quick as possible, even if its a Mig-31.
When your weapons are depleted, you head back to base, as fast as possible, there might be bandits on your six, so no time to hang about.

according to this chart posted in keypub
Image
mig-31 turn very slow , around 1 degree per second at mach 2.2 , 55K feet
Previous

Return to Military Aircraft of the Cold War

Who is online

Users browsing this forum: No registered users and 6 guests