f-16 variable intake

Unread postPosted: 09 Aug 2019, 03:01
by rowbeartoe
Hi Everyone.

Question, why doesn't the F-16 have a variable intake like the F-15? Wouldn't it give the F-16 some advantages for speed? Same question for all of the F-18 Jets (A-F).

Thank you everyone.

Re: f-16 variable intake

Unread postPosted: 09 Aug 2019, 03:32
by sprstdlyscottsmn
Cost, weight, maintenance, didn't need them to meet mission objectives. That's the long and short of it.

Re: f-16 variable intake

Unread postPosted: 13 Aug 2019, 05:53
by boilermaker
rowbeartoe wrote:Hi Everyone.

Question, why doesn't the F-16 have a variable intake like the F-15? Wouldn't it give the F-16 some advantages for speed? Same question for all of the F-18 Jets (A-F).

Thank you everyone.

F16N of aggressor had a bigger intake with a significant thrust increase but not speed increase. On the F16 a variable intake would require to vary the nose length, I believe, which is not really practical.

That being said,the splitter plate or variable plates on the F15 are old tech. The divertless intake is what would be used in the future such as on the F35.

https://en.m.wikipedia.org/wiki/Diverte ... onic_inlet

Re: f-16 variable intake

Unread postPosted: 13 Aug 2019, 12:42
by madrat
boilermaker wrote:That being said,the splitter plate or variable plates on the F15 are old tech. The divertless intake is what would be used in the future such as on the F35.


Which would be a good way to integrate the targeting pod underneath the nose of future build and SLEP F-16s. Free up some drag-inducing space. It would be nice to see F-16's piggy back off any F-35 derived drop tanks, too, to simplify inventories as F-16s age out. Where's the sugar daddy to pay for all these features?

Re: f-16 variable intake

Unread postPosted: 13 Aug 2019, 12:54
by basher54321
boilermaker wrote:F16N of aggressor had a bigger intake with a significant thrust increase but not speed increase. On the F16 a variable intake would require to vary the nose length, I believe, which is not really practical.

That being said,the splitter plate or variable plates on the F15 are old tech. The divertless intake is what would be used in the future such as on the F35



Incorrect - the F-16N was an early block 30 with the smaller or Normal Inlet so actually had reduced thrust compared to the big mouth inlet on later block 30s.

The F-16 79 had a different inlet which helped it increase top end speed.

if they needed an m2.2 top end then fairly sure it would have got a variable inlet.

Re: f-16 variable intake

Unread postPosted: 14 Aug 2019, 04:58
by boilermaker
Ok, some corrections


https://www.thedrive.com/the-war-zone/3 ... ary-hotrod

"
The Navy’s Hotrod Viper

The F-16N looked like an F-16C block 30 airframe, powered by the General Electric F110-GE-100 engine with 25,735 pounds of thrust in full afterburner. It normally weighed less than 25,000 pounds with full internal fuel. Later blocks of F-16s had a larger air intake, because that was apparently a limiting factor for the GE engine. With the bigger intake the engine could develop almost 29,000 pounds of thrust.
"

Re: f-16 variable intake

Unread postPosted: 14 Aug 2019, 13:20
by basher54321
You will find all the F-16Ns in the database here - as far as the airframe goes they were designated Block 30B to Block 30E

e.g

http://www.f-16.net/aircraft-database/F ... file/2192/

Re: f-16 variable intake

Unread postPosted: 21 Aug 2019, 19:23
by n3sk
I believe General Dynamics actually designed a variable inlet but never made it out of the filing cabinet. Had the program requirements needed more speed they could have. My arm chair general knowledge would lead me to believe at the time F-15 has that performance metric covered, so it was redundant to give the F-16 such ability. If you want more speed F-15 was the answer.

Also didn’t the F-16 suffer from yaw stability issues at high speed? One of the reasons they added these.

Re: f-16 variable intake

Unread postPosted: 21 Aug 2019, 21:36
by johnwill
I don't know if you would say they were added, since the YF-16 had them also. They were added in the same way wings and tails were added during the preliminary design phase. Like most airplanes, F-16 control surfaces lose effectiveness as mach number increases. So, yes, the ventrals were included in the original design to make up for reduced rudder/vertical tail yaw effectiveness at supersonic conditions. F-16XL did not have ventrals, since the extended aft fuselage left no room for runway clearance.

F-5, T-38, and F-15 dealt with loss of rudder/vertical tail yaw effectiveness by using very short rudders, only about half of tail span. A rudder in the upper part of the tail would twist the tall skinny tail reducing its effectiveness in the same way ailerons can reduce or even reverse roll control.

Re: f-16 variable intake

Unread postPosted: 21 Aug 2019, 23:14
by n3sk
Excuse my improper terminology. Imagine some of this information presented on this site https://www.secretprojects.co.uk/thread ... f-16.1335/ has been discussed but thought it might add to the topic. Also I find it interesting how much the last picture with the twin tail and dual side mounted intakes looks like F-35.

Re: f-16 variable intake

Unread postPosted: 21 Aug 2019, 23:19
by basher54321
n3sk wrote:My arm chair general knowledge would lead me to believe at the time F-15 has that performance metric covered, so it was redundant to give the F-16 such ability. If you want more speed F-15 was the answer.


Not sure about that considering the majority of potential F-16 customers had no access to the F-15 for one reason or the other. Or even that according to some of John Wills colleagues the downgraded for export F-16 J79 was taken over M2.1 in level flight with no control or stability issues.

According to Hillaker the requirement for acceleration in areas where combat was actually taking place was far more important to the USAF than a M2.2 - M2.5 top speed.

Re: f-16 variable intake

Unread postPosted: 22 Aug 2019, 00:24
by johnwill
Buckner's notes on the YF-16, Item 4, mention a simple inlet with no moving parts. In fact, in order to try to improve inlet performance at high power, low airspeed conditions (takeoff, for example) a pair of blow-in doors was installed on the upper surface of the inlet, just under the cockpit. They were approximately 8 x 12 inches, hinged at their leading edges. A couple of months into the Light Weight Fighter flyoff, they were bolted shut, as they did not provide any significant help.

Re: f-16 variable intake

Unread postPosted: 22 Aug 2019, 03:33
by boilermaker
n3sk wrote:Excuse my improper terminology. Imagine some of this information presented on this site https://www.secretprojects.co.uk/thread ... f-16.1335/ has been discussed but thought it might add to the topic. Also I find it interesting how much the last picture with the twin tail and dual side mounted intakes looks like F-35.


Vg-FX looks like a Flanker with variable geometry wings... would they have gotten this data and used it to make the tlanker?