Can the Turkey pull a cobra?

[Coyote Duster]

Edited September 26, 2016 by SkateZilla

[BlackLion213]

Not really from what I have read. Flight testing demonstrated transient AOA readings of around 40 degrees (I don't have the source near me - I think it was degrees and not units) during level flight nose pitch up maneuvers that were still controllable. Wings level transient AOA readings can be higher without control issues than banked AOA readings, but the Tomcat does not have the high AOA capability of the Flanker or Hornet.

 

As an indication of expected performance, the AOA gauge pegs at 30.

 

Pitch authority and high AOA stability are better with the wings swept (stability meaning less wing drop, but harder to judge the transition to departure), but trying to generate really high AOA at speeds where the wings are swept (according to the wing sweep program of the air-data computer - not manual) tends to generate G forces above the max rating of the airframe. You could perform a high AOA maneuver with the wings swept at lower speeds, but the airframe really bleeds airspeed and there are fewer warnings before control departure (an issue when Tomcats would perform over-ship breaks during CAT III recoveries - they had to watch the AOA guage carefully). Also, though AOA may be higher with the wings swept at lower speeds, the resulting rate and radius of the turn will be inferior to that of the wings swept forward.

 

There are plenty of pilot reports of higher AOA during low speed ACM maneuvers, but these often led to control departures (or were pitch up events once the aircraft had departed).

 

The real Cobra requires AOA in excess of 90 degrees.

 

https://en.wikipedia.org/wiki/Pugachev%27s_Cobra

 

Fortunately, the Tomcat generates excellent turn performance at lower AOA than most modern fighters, largely because of it's large, relatively straight wing.

 

The Tomcat in that video is probably 45 deg of AOA or less from what I can tell.

 

-Nick

 

PS - Disclaimer: the above post is based on my readings of pilot tales and F-14 literature. I don't have NASA tables or official aerodynamic data.

Edited August 18, 2016 by BlackLion213

[Coyote Duster]

Not really from what I have read. Flight testing demonstrated transient AOA readings of around 40 degrees (I don't have the source near me - I think it was degrees and not units) during level flight nose pitch up maneuvers that were still controllable. Wings level transient AOA readings can be higher without control issues than banked AOA readings, but the Tomcat does not have the high AOA capability of the Flanker or Hornet.

 

As an indication of expected performance, the AOA gauge pegs at 30.

 

Pitch authority and high AOA stability are better with the wings swept Stability meaning less wing drop, but harder to judge the transition to departure), but trying to generate really high AOA at speeds where the wings are swept (according to the wing sweep program of the air-data computer - not manual) tends to generate G forces above the max rating of the airframe. You could perform a high AOA maneuver with the wings swept at lower speeds, but the airframe really bleeds airspeed and there are fewer warnings before control departure (an issue when Tomcats would perform over-ship breaks during CAT III recoveries - they had to watch the AOA guage carefully). Also, though AOA may be higher with the wings swept at lower speeds, the resulting rate and radius of the turn will be inferior to that of the wings swept forward.

 

There are plenty of pilot reports of higher AOA during low speed ACM maneuvers, but these often led to control departures (or were pitch up events once the aircraft had departed).

 

The real Cobra requires AOA in excess of 90 degrees.

 

https://en.wikipedia.org/wiki/Pugachev%27s_Cobra

 

Fortunately, the Tomcat generates excellent turn performance at lower AOA than most modern fighters, largely because of it's large, relatively straight wing.

 

The Tomcat in that video is probably 45 deg of AOA or less from what I can tell.

 

-Nick

 

PS - Disclaimer: the above post is based on my readings of pilot tales and F-14 literature. I don't have NASA tables or official aerodynamic data.

 

thanks for the explanation

[ebabil]

sorry to ask but what does this has to do with Turkey?

[probad]

iirc the tomcat was known as the turkey because when they check the control surfaces before takeoff all the moving tail surfaces reminded some people of a turkey's mass of tailfeathers

 

its got nothing to do with the country.

[Harpoon]

sorry to ask but what does this has to do with Turkey?

 

"Can the Turkey pull a cobra?"

"the Turkey" is much different than "Turkey" by itself.

 

edit: seems like i was sniped by a day.

[jcdata]

Planned departures made the f14 a dangerous combatant in the gun match. Cartwheels, snap rolls etc to point the nose where you wanted it.

 

Sent from my XT1585 using Tapatalk

[Pocket Sized]

On the topic of sudden, possibly catastrophic pulls on the stick, how easy is it to over G the Tomcat? AFAIK the FCS is mostly just boosting the stick movements through hydraulics.

[turkeydriver]

Easy, if you got the Schlitz on the jet and the muscles to snap it. Watch airshow vids from crew perspective- you can here the RIO remind the pilot to "watch the G" coming out of every dive. Hoser Satrapa put +10g in a defensive break that produced an "aluminum cloud" to break Hawk Smith's track during AIMVAL/ACEVAL. A plane captain from a reserve squadron reported seeing +12g. It all depends on the speed of the jet when you make that hard pull.

[Hummingbird]

Well, you decide:

 

We1T-FxY9Bs

 

As far as I know the further back the wings were the less safe it was to do the very high alpha maneuvers (in excess of 30 deg) in the F-14 due to issues with lateral stability.

With wings swept forward however the aircraft was a lot more stable, and it seems as though it could approach 80-90 deg alpha without departure under symmetrical loads.

Edited September 24, 2016 by Hummingbird
Condensed two posts into one

[Basher54321]

Any details on the video? - Is that not the Yaw vector test bed?

[Basher54321]

You can do more than one thing with an airplane.

 

Sorry not sure what you mean by that.

 

In the mid 80s an F-14A was modified with Yaw Vectoring and apparently demonstrated full control near 90 degrees alpha.

 

If not the video demonstrates the F-14A(?) could attain brief transient AoA near 90 degrees anyway (without the same control level).

[Goblin]

Pugachev's Cobra is possible because of the pilot is able to turn off the part of the flight computer that controls control surface speed and travel to prevent departure from controlled flight. Turning this off gives the pilot the ability to rotate the horizontal surface beyond the point where AoA would be considered stalling, and do so very rapidly.

 

Also, Pugachev's Cobra goes beyond 90 degrees pitch up.

 

And it can be performed with aircraft without flight computers...

BTW, the SAAB J35 Draken did it way before Pugachev did it in the Su-27.

:pilotfly:

 

[Xenovia]

And it can be performed with aircraft without flight computers...

BTW, the SAAB J35 Draken did it way before Pugachev did it in the Su-27.

:pilotfly:

 

 

but only at high altitude can the Draken achieve it.

[Goblin]

but only at high altitude can the Draken achieve it.

 

No.

But it has a nasty tendency to enter a superstall, so it's not advicable to do it at lower altitudes. :)

[MikeMikeJuliet]

On the tomcat videos... Although the aircraft gies pretty much 90 degrees nose up, it looks to me like it starts to climb quite quickly before the highest nose-up attitude is reached, which would give us an AOA that is significantly lower than 90. Though that is just what I saw from the videos and there are not too many reference points to compare the AOA to.

 

So to me, does not yet look like a full cobra. Just my observation though.

[SkateZilla]

This is called Maximum Performance Pitch out, The Ability to Drastically change direction and accelerate away from the initial point using aggressive pitch.

 

Not a Cobra.

Edited September 26, 2016 by SkateZilla

[Basher54321]

So to me, does not yet look like a full cobra. Just my observation though.

 

Might be a good observation

 

Rapid expansion in high AOA capability (due in part to advances in flight control system integration required for use with relaxed static or statically unstable longitudinal designs and in part to improved aerodynamic design) was first exploited by the F-14A Tomcat and exceeded the

design areas covered by MIL-F-8785C. When this specification was first introduced, high AOA was considered to be about 16 degrees. The F-14 expanded that to over 50 degrees, although the Tomcat did not have the control power to exploit this region.......The F-14A can safely be maneuvered to 50 degrees AOA...

 

Operational Lessons Learned from the F/A-18E/F (2000, USN/NAS)

[Hummingbird]

It does look like the F-14 pulls off a near cobra maneuver in one of the video clips, there seemingly beeing little change in altitude. Not sure it qualifies as an actual cobra however, looking at the Su-27 or Draken pulling off the maneuver they often go as far as 100-110 deg.

[SkateZilla]

It does look like the F-14 pulls off a near cobra maneuver in one of the video clips, there seemingly beeing little change in altitude. Not sure it qualifies as an actual cobra however, looking at the Su-27 or Draken pulling off the maneuver they often go as far as 100-110 deg.

 

The Videos of the Test Aircraft doing it there is a significant change in altitude.

[Hummingbird]

The Videos of the Test Aircraft doing it there is a significant change in altitude.

 

Depends on which sequence we're talking about. In the first three you cannot tell wether there's a significant change in altitude, infact it looks as though it isn't very much.

 

But obviously, and as you see in the other clips, the slower the pitch up the greater the gain in altitude, and the remaining sequences show the aircraft pitching up at a slower rate than the first two or three.

 

Either way I think we can all agree that it isn't a true cobra maneuver, but tbh the speed probably wasn't low enough for that to even be possible anyway.

Edited October 3, 2016 by Hummingbird

[Gierasimov]

...or even more...

 

It does look like the F-14 pulls off a near cobra maneuver in one of the video clips, there seemingly beeing little change in altitude. Not sure it qualifies as an actual cobra however, looking at the Su-27 or Draken pulling off the maneuver they often go as far as 100-110 deg.

 

F-14 was not even near Pugachev's Cobra at all --

 

F-22 on the other hand was a bit closer but maneuver looks rough compared to Su-27 or MiG-29...

 

[SkateZilla]

F-14 was not even near Pugachev's Cobra at all --

 

F-22 on the other hand was a bit closer but maneuver looks rough compared to Su-27 or MiG-29...

 

 

The U.S. Puts Restrictions on what Pilots can do in Airshows.

 

You will not see a "cobra" performed by a western fighter over a populated area.

 

 

And that First Video was from a Video Game (Battlefield 3), not Real life.

 

A "Cobra" is not a Literally Horizontal Only Maneuver, there is some altitude change.

[Goblin]

Check this vid @ 1:50

[SkateZilla]

there was altitude change, the 1st angle wasn't noticeable because he rolled out, so the change in elevation was more along the horizon instead of vertical