View Full Version : Thrust Vectoring Effect on Rate of Turn
Hi everyone
I just got a question after reading my old POF book. the Eqaution for rate of turn: ROT = 1,091 x tangent of the bank angle / airspeed
How would that change when the airplane is equipped with Thrust Vectoring?? like the F22 og SU35???? Does anyone has an equation for that??
chevvron
15th Feb 2021, 08:36
Works on the Harrier.
Mogwi
15th Feb 2021, 09:03
Actually, on the Harrier it increased the pitch rate, which gave an instantaneous increase in rate of turn BUT this caused a loss of airspeed with the resultant reduction in rate of turn.
Usefull to generate angles and force a fly-through but at the cost of a massive loss of energy.
Happy days!
Mog
Actually, on the Harrier it increased the pitch rate, which gave an instantaneous increase in rate of turn BUT this caused a loss of airspeed with the resultant reduction in rate of turn.
Usefull to generate angles and force a fly-through but at the cost of a massive loss of energy.
Happy days!
Mog
Loss of airspeed would result in a higher rate of turn...
ShyTorque
15th Feb 2021, 10:30
Loss of airspeed would result in a higher rate of turn...
I think Mogwi might know quite a lot about this, having been one of the very few pilots to have actual air combat experience on the type! In 1982....
Easy Street
15th Feb 2021, 10:41
Loss of airspeed would result in a higher rate of turn...
It’s a bold move to attempt to correct someone offering the benefit of their experience with a statement that belies so little knowledge, especially when that person is a combat-experienced Harrier pilot! Your quote above is only true at a fixed bank angle at zero pitch rate above stalling speed; you might consider taking some elementary training in steep turning. In combat, turning is achieved by rolling to point the lift vector in the desired direction and pulling to attain maximum lift (and therefore turning performance). Maximum attainable turn rate rises with airspeed until Vc or ‘corner speed’ because the increase in available lift (a factor of V-squared and part of the numerator in a turn rate equation) dominates the calculation (in which the denominator is a factor of V). Turn rate decreases above Vc as structural load limits prevent additional lift from being applied.
Pugilistic Animus
15th Feb 2021, 11:04
1091VTAN Phi is dependent only based upon bank the bank angle, no matter how that particular bank angle was achieved, including a thrust vector component to the bank angle.
ExAscoteer2
15th Feb 2021, 11:46
Wow! That's pretty arrogant arguing with a Combat Experienced Harrier Jock!
Pugilistic Animus
15th Feb 2021, 12:02
It doesn't contravene him at all...just a slight addition.
heights good
15th Feb 2021, 14:29
Wow! That's pretty arrogant arguing with a Combat Experienced Harrier Jock!
It still doesn't mean he is correct :)
I have 10 combat tours under my belt but I still have stuff to learn from others, to think otherwise is a tad arrogant.
p.s. I have no idea who is correct.
ASRAAMTOO
15th Feb 2021, 15:11
The Harrier has been around a while so I'm sure what Mogwi said is correct. But lets examine a hypothetical future aircraft.
The Harrier needs all of its thrust to sustain a high g turn. If you use some of this thrust to temporarily increase pitch rate then speed falls off. A future aircraft might be able to sustain limiting g at less than full power. If this is the case and it is capable of thrust vectoring, then the forward component of thrust may still be able to sustain limiting g whilst leaving some thrust spare to generate nose angle. Obviously its a little more complicated than that in that alpha is also likely to increase which will have a significant effect on drag and there may no longer be 'spare' power available to generate nose angle.
Pugilistic Animus
15th Feb 2021, 16:09
Just to add: kinematics is the study of motion independent of the applied forces that cause the motion. 1091VTAN Phi is a kinematic relation:)
Easy Street
15th Feb 2021, 16:11
the forward component of thrust may still be able to sustain limiting g whilst leaving some thrust spare to generate nose angle. Obviously its a little more complicated than that in that alpha is also likely to increase which will have a significant effect on drag and there may no longer be 'spare' power available to generate nose angle.
In such a situation the ‘upward’ component of thrust would be added to the lift vector. This would instantaneously reduce the alpha (as the flight path would be changed ‘upwards’ with respect to the oncoming airflow) which would reduce lift (and turn rate), requiring additional nose-up control input to regain and then maintain the target alpha. The ability to make this control input manifests as “nose pointing” capability but in the hypothetical sustainable case it can also be seen as increasing the turn rate. In turn, the additional nose-up control input requires the thrust vector to be rotated slightly aft to sustain forward speed. A complex equilibrium would eventually be reached with not quite as much benefit as a ‘static’ analysis of the available excess thrust vector might suggest.
Other “nose pointing” effects may result from the thrust vector producing a rotational moment around the CofG. This is what I think you were getting at with your reference to increasing alpha, but it is actually an installation-specific effect.
1091VTAN Phi is dependent only based upon bank the bank angle, no matter how that particular bank angle was achieved, including a thrust vector component to the bank angle.
2 items
.1 Your simplified calcilation is valid only for a level turn.
2. Vectoring adds an additonal force to that only from bank angle
Pugilistic Animus
15th Feb 2021, 21:43
FDR if you please, may you elaborate? I don't think that I'm understanding you correctly for The gTan Phi limitations
Pugilistic Animus
16th Feb 2021, 01:52
Loss of airspeed would result in a higher rate of turn...
Yes, From your our primary training.... remember how during slow flight when the turn coordinator showed a high rate turn? If you choose to turn in the first place gotta give her slightly higher power setting and then you can safely commence that turn with a five or ten degree bank angle...just for general interest, the turn radius at the stall is infinite. :)
DCThumb
16th Feb 2021, 05:45
The Harrier has been around a while so I'm sure what Mogwi said is correct. But lets examine a hypothetical future aircraft.
The Harrier needs all of its thrust to sustain a high g turn. If you use some of this thrust to temporarily increase pitch rate then speed falls off. A future aircraft might be able to sustain limiting g at less than full power. If this is the case and it is capable of thrust vectoring, then the forward component of thrust may still be able to sustain limiting g whilst leaving some thrust spare to generate nose angle. Obviously its a little more complicated than that in that alpha is also likely to increase which will have a significant effect on drag and there may no longer be 'spare' power available to generate nose angle.
Surely if an aircraft is turning at the limiting G, increasing the pitch rate, no matter how you do it will exceed the limiting G?
beardy
16th Feb 2021, 06:31
.just for general interest, the turn radius at the stall is infinite. :)
Wouldn't that only be true if the lift at the stall was zero in a stable environment without thrust vectoring?
Easy Street
16th Feb 2021, 06:54
Surely if an aircraft is turning at the limiting G, increasing the pitch rate, no matter how you do it will exceed the limiting G?
I was going to say something about that in one of my earlier posts but they got a bit long. The short answer is yes. However the 'upwards' component of the thrust vector contributes to the increase in pitch rate without increasing wing loading (lift is constant if speed and alpha are maintained) so the increase in load factor only applies to other parts of the airframe. So such a system would only be useful if structural limits were based on the wings or their attachment points.
PA,
there are various methods of TV, and TVC applied.
1. Harrier: 2-D split cold/hot exhaust, vectoring angles are downward relative to the aircraft longitudinal axis, giving a variable from thrust, or positive force normal to the longitudinal axis, or a combination of that or similar with a deceleration component. Viffing adds a vertical force that decouples the turning rate from the angle of the bank partially, still requires a vector in the desired turn, but the total normal force is a combination of lift and any thrust vectoring. Comes with some costs in EM state.
2. Sukhoi, limited axisymmetrical TVC. Gives increased agility, adds control authority to extend instantaneous rates to point nose. Has a force component for pitch rates, but that is also partially opposite the normal force from lift... for a pitch up by vectoring exhaust nozzles upwards, total lift force from the wing and body has to be increased to counter the negative component of the TVC vector. Not a problem if you have big wing areas and can generate reasonable CL/AOA. Instantaneous rate of turn is the benefit. Normal vectoring angles are around +-20 degrees from the longitudinal axis. Provides roll as well as yaw potential.
Note: any pitch TVC will increase wing bending load for a given g limit, the thrust counters the aerodynamic force required to achieve the total normal force to get the g... so TVC does come with a structural penalty, but great offsets.
3. F-22. 2-D, low RCS TVC. drops the yaw ability. Could do roll augment.
4. F-35: 2-D has a dedicated cold fan lift for TO/LDG, but does have the potential for TVC but is not indicated to be implemented. If it was it could be 2D or axisymmetric, with pitch and yaw, no roll. The design of intake suggests that it is not intended to do the Harrier Viffing deal.
5. J10B TVC: axisymmetrical TVC demo'd in 2018.
6. USSR, Yaks etc... dedicated lift engines, and always had a potential for pitch augmentation.
The F-22 has a Type III TVC nozzle which is in keeping with low RCS, all of the others, have type I nozzles.
Re g limits, only the harrier type TVC can unload the wing while achieving a given g loading. The g load limit may have a constraint on the flight control systems or fuselage itself but it is usually the wing bending load that determines the limit. Mixed design bag, the weight saved in the structure is offset by the weight of the cold exhausts and the total power plant installation weight. The AV8B had lots of potential to improve TVC ability... still a neat plane.
Schneider (1988) was mainly talking about the AV8 type design, and stated:
"the results indicate that the use of vectored thrust to supplement the aircraft's lift by directing the thrust into the turn can substantially reduce turning times and increase in-flight maneuverability".
That is a valid statement for an in-flight lift design, which most current designs are not, they instead have gone to the pitch augmentation which gives instantaneous rate enghancement, but detracts from available lift for a given AOA (yes, it also gives more AOA capability, so other than the buckets of drag... etc... structurally, the wing has to be stronger than a non pitch augmenting TVC design.
The AV8 would have had intersting potential for extreme agility with a bi 'o mixing of the nozzles, and throw in an ACM mix of RCS as well...The F-35 not implementing TVC is curious, even a TYpe III nozzle wouldn be worthwhile or a Type IV fluidic on any exhust would be entertaining for instantaneous rates.. In inpinging flow would also direct the exhaust, there was some interesting work in htat area in the early 90s, but was not directed to giving improved agility to aircraft. (did a bit of that on a Learjet exhaust, which was working on acoustic supression, ended up getting an effect similar to exhaust wedges, but without the EGT rise, was all going well until it didnt, and then we got to remake the devices and redo it, and repaint the nacelle).
https://cimg2.ibsrv.net/gimg/pprune.org-vbulletin/1286x1084/screen_shot_2021_02_16_at_8_55_18_pm_1f28f33b58b8a5c440144da 7be2e2199737d9aad.png
good reading at:
Snow, B. (1990). Thrust Vectoring Control Concepts and Issues. SAE Transactions, 99, 1488-1499.
Lee, P.H., Lan, C. E., (2012) Effect of thrust vectoring on level-turn performance. AIAA J. Aircraft, vol 29 (3) Engineering Notes
Schneider, G.L Watt, G.W., (1988) Minimum-Time Turns Using Vectored Thrust . AIAA J. Guidance,
Victoria, R., Gatlin, D., Kempel, R., Matheny, N., The F-18 High Alpha Research Vehicle: A High-Angle-of-Attack Testbed Aircraft, NASA TM-104253, Sept. 1992.
Canter, D., "X-31 Post-Stall Envelope Expansion and Tactical Utility Testing," Fourth NASA High Alpha Conference, NASA CP-10143, vol. 2, July 1994.
Kidman, D. S., Vickers, J.E., Olson, B.E., and Gerzanics, M.A., Evaluation of the F-16 MultiAxis Thrust Vectoring Aircraft, AFFTC-TR-95-12, Sept. 1995
Orme, J. S., Hathaway, R., and Ferguson, M.D., Initial Flight Test Evaluation of the F-15 ACTIVE Axisymmetric Vectoring Nozzle Performance, NASA TM-206558, July 1998
Pugilistic Animus
16th Feb 2021, 13:49
Whoa yes! Thank you FDR, I actually never knew about decoupling thrust moments from bank angle to increase rate of turn. I do have access to a wonderful library, so I could definitely look at further reading.
I'm much more of a wing guy and not much of a propulsion guy other than aerothermodynamics of engines. , although lately, as far as teaching is concerned. I deal mainly with thermodynamics 1&2. I appreciate the time you took responding in detail. There are a couple of acronyms I don't know yet but I'll look them up.
Once again, many thanks
Easy Street
16th Feb 2021, 14:16
The AV8 would have had intersting potential for extreme agility with a bi 'o (?) mixing of the nozzles,
I think I know what you are getting at! John Farley proposed it in the mid 1970s but sadly never got anywhere. See pp123-124 here (https://www.rafmuseum.org.uk/documents/research/RAF-Historical-Society-Journals/Journal-35A-Seminar-the-RAF-Harrier-Story.pdf).
Salute!
Great thread.
I go with Easy, Mog and FDR. In my limited A2A experience in the Viper, about the only advantage we could see with TV was nose-pointing ability. My Harrier buddy that also flew Slufs and Vipers and Thuds had the same view as Mog.
Secondly, once in the the fight, bank angle is only a biggie if the other guy is not turning in the same plane as you. So the equation needs to take out that factor. OTOH when at zero or close to zero bank angle, God's gee helps or hurts depending if inverted or not. The old "egg" they show you about tighter turn over the top and such. Once turning and going thru all the points on the protractor, you are mainly putting the lift vector where you need to to get a shot or close on the bandit. The F-22 uses TV primarily for nose-pointing from what I have heard. Mainly we could get a Raptor pilot to comment or someone who has engaged a Raptor.
Gums sends...
Salute!
Secondly, once in the the fight, bank angle is only a biggie if the other guy is not turning in the same plane as you. So the equation needs to take out that factor. OTOH when at zero or close to zero bank angle, God's gee helps or hurts depending if inverted or not. .... Once turning and going thru all the points on the protractor, you are mainly putting the lift vector where you need to to get a shot or close on the bandit. The F-22 uses TV primarily for nose-pointing from what I have heard.
Gums sends...
If you want higher roll rates, the Gums Special leading edge device is pretty effective... use once only and discard.. :}
Up in area where 3D maneuver is possible, each driver is trying to get out of plane with the other at the cost of energy loss. The start will have reasonable energy, and altitude permits recovery of energy loss from a bout of TV. Whatever your ride, you are going to be either forced or dragged down to the weeds over time, and then a TV may get the solution, at the cost of loss of energy.
Gods g by pegasus is about the addition that the harrier had available, with a really large speed brake effect.
musings....
Sustained turn factors:
stall speed
L/D
excess thrust
structural g limit
high aoa stability & control
Reducing stall speed and improving L/D is possible, even while retaining RCS. That gives a smaller turn radius as well as increased rates of turn which can. be helpful,
The 15, 16, and 18 testbeds had various methods of giving TV, but the petal style X-31 Type III system would suggest that upgrade could be done to existing variable nozzles, but they have some geometry issues for retrofitting. Going to Type IV fluidic type wake vectoring would fit within current variable nozzles, would be a relatively lightweight and cost-effective complication to the other team.
manoeuver capability is always going to remain a factor in force capability. Pre merge engagement does not have a sufficiently high Pk to avoid leakers, so as even just a defensive follow-up it will be important. The rate of turn capability is supplemented where the missiles onboard your ride have an over-the-shoulder capability, and if the red team has that, then that increases the importance of first kill, turn rate, IR suppression/ IR countermeasures, etc. If you find sustainer type boost sections being added to your AMRAAM/R-77 etc, then its time to retire, If the missile has a first stage that has gimbal and throttling or low specific impulse, then the ability to get a near 180 degree turn off the missile starts to be achievable, designated by a helmet-mounted sight, that would be a good time to become a drone pilot.
Salute!
Secondly, once in the the fight, bank angle is only a biggie if the other guy is not turning in the same plane as you. So the equation needs to take out that factor. OTOH when at zero or close to zero bank angle, God's gee helps or hurts depending if inverted or not. .... Once turning and going thru all the points on the protractor, you are mainly putting the lift vector where you need to to get a shot or close on the bandit. The F-22 uses TV primarily for nose-pointing from what I have heard.
Gums sends...
If you want higher roll rates, the Gums Special leading edge device is pretty effective... use once only and discard.. :}
Up in area where 3D maneuver is possible, each driver is trying to get out of plane with the other at the cost of energy loss. The start will have reasonable energy, and altitude permits recovery of energy loss from a bout of TV. Whatever your ride, you are going to be either forced or dragged down to the weeds over time, and then a TV may get the solution, at the cost of loss of energy.
Gods g by pegasus is about the addition that the harrier had available, with a really large speed break effect.
musings....
Sustained turn factors:
stall speed
L/D
excess thrust
structural g limit
high aoa stability & control
G-LOC
Reducing stall speed and improving L/D is possible, even while retaining RCS. That gives a smaller turn radius as well as increased rates of turn which can. be helpful,
The 15, 16, and 18 testbeds had various methods of giving TV, but the petal style X-31 Type III system would suggest that upgrade could be done to existing variable nozzles, but they have some geometry issues for retrofitting. Going to Type IV fluidic type wake vectoring would fit within current variable nozzles, would be a relatively lightweight and cost-effective complication to the other team.
manoeuver capability is always going to remain a factor in force capability. Pre merge engagement does not have a sufficiently high Pk to avoid leakers, so as even just a defensive follow-up it will be important. The rate of turn capability is supplemented where the missiles onboard your ride have an over-the-shoulder capability, and if the red team has that, then that increases the importance of first kill, turn rate, IR suppression/ IR countermeasures, etc. If you find sustainer type boost sections being added to your AMRAAM/R-77 etc, then its time to retire, If the missile has a first stage that has gimbal and throttling or low specific impulse, then the ability to get a near 180 degree turn off the missile starts to be achievable, designated by a helmet-mounted sight, that would be a good time to become a drone pilot.
Salute!
Good points, FDR.
When you do the Boyd type equations and tactics, then try to fly them, I found that the turn rates and some of the nose pointing was better in the Viper due to the stabilators increasing lift toward the center of your turn regardless of bank angle. Let's face it, no body fights in a bandit gathering level turn regardless of how many gees you can pull or your turn rate. So more lift toward the center helps you, and my rule of thumb equation is decent.
gee=vee^2/radius where radius can be derived using speed and turn rate radius=vee/rate
You can see that the converse can be used to get either radius or rate. And guess what? The more gee you can pull without stalling has a good effect on rate or radius.
I first noticed the nose pointing issue when flying versus the Eagle at slow speed. Stall was not a limit for either of us, but our AoA limiter was a biggie. Ditto versus the Hornet or Tomcat.
So maybe the thread should emphasize body rate versus turn rate, as a delta like I flew early on could move that nose at obscene rates and I wasn't turning in space worth a hoot! And was rapidly becoming a strafe target for the bandit's wingman.
... Gums sends...
heights good
17th Feb 2021, 01:41
Just to bring this thread back to my level of comprehension and intellect, I like boobs! :}
flighthappens
17th Feb 2021, 01:56
Up in area where 3D maneuver is possible, each driver is trying to get out of plane with the other at the cost of energy loss. The start will have reasonable energy, and altitude permits recovery of energy loss from a bout of TV...
Based on what?
Based on what?
Fair point.
(I'm in isolation during an engine change so my boredom may show through in the following)
background:
T/W gives a starting point for an E-M analysis, which is relatively straightforward although it is dependent on the loadout and fuel state.
Excess thrust is variable to aoa and to wing planform, and load drag count.
Wing loading trumps almost everything.
As the great gummed one will note this is one of the E-M graphs that he would have been familiar with, and that is for the small mouth, but lightweight plane, as Boyd fought for. This is for mid-levels. At lower levels, thrust increases... and the energy deficit region shifts to higher turn rates. Energy Maneuverability AD372287 (1966) from APG Eglin, FL (that's John Boyds, Tom Christie's, and James Gibson's handiwork) gives enough data to set out altitude effects. (The profound effect of wing loading is evident in the turn performance of the MiG21 v the F4C, as while the planform of the MiG-21 is a high drag form, and the installed thrust gives inferior level acceleration (forget about the pre -bis low altitude vertical stab buffet... ) it gives the mod delta of the F4 a run for its money in turn.
Your Typhoon has lots of thrust... the wing is a relatively high drag, but it is a low wing loading and lightly loaded it has spectacular performance and agility. the Rafale is close to the same down low. Either of these will give an F-16 a serious run for their money. If the F16 has to go past a merge, it will be losing height to maintain a position that doesn't go defensive promptly. The F-18 will want to be very careful to avoid a furball. The 15EX would be interesting to assess on available data. The F-22 will still give both the EFA and Rafale a hard time. The F-35 will be wanting to take out the targets before the merge on available data.
To achieve a high sustained rate of turn, the former gold standard will eventually start to trade altitude, or will drop some rate but will eventually bleed speed,
As for the start of a furball, tactics will determine engagement height but physics will guide the tactics. Missile range is dependent on density; potential energy affects options; (the question asked); altitude alters AAI radar detection range and air defense radar....; the presence of SAM, AAA, terrain all impact the likely fragged profile, along with logistics of range/AAR constraints. Lots of variables, even the profiles that various forces train for. Presumably, an algorithm can be put out to give a probability plot of the likely approaches, heights, and force compositions, but then Sun Tsu gets a nod on the impact of surprise, so, yeah, your question is quite fair.
A defensive manoeuver for missile defense where you are up in the blue is likely to incorporate a lateral manoeuver to force a turn rate on the missile, and a change of altitude to increase the drag of the missile to reduce its velocity post booster burnout. A descent will achieve the latter and retain the energy state of the defensive aircraft.
https://cimg2.ibsrv.net/gimg/pprune.org-vbulletin/1252x1174/screen_shot_2021_02_17_at_7_57_53_pm_0be66d327b7c9e36c4b83e5 0c1d8c65377dba596.png
In 1964, Boyd & co put out these E-M charts.... gotta love their work
Comparison of Brand X v Brang Y:
https://cimg0.ibsrv.net/gimg/pprune.org-vbulletin/1174x722/screen_shot_2021_02_17_at_10_00_08_pm_14b3a2fd9d6754cb39fb8c 405c76159c2033e927.png
BRAND X
https://cimg3.ibsrv.net/gimg/pprune.org-vbulletin/1220x710/screen_shot_2021_02_17_at_10_00_15_pm_bdd0102b502b1ba8d6ec7b 8a400a4fee045ccfa8.png
BRAND Y
This matrix covers thrust vectoring solutions. I was thinking of adding the original equations that Boyd and Christie used, it is entertaining, but the quality is so bad of the copy that it need not have been declassified :} Heck, I couldn't resist... it's a bit of the minimum time to climb solution the boys from Eglin did using Bryson & Denholns optimal programming method. doctors handwriting...
https://cimg7.ibsrv.net/gimg/pprune.org-vbulletin/1860x510/screen_shot_2021_02_17_at_9_56_58_pm_a2f3dd5eafaa6e5ac262b68 ba2d215aee00966f5.png
Bryson and Denham, 1962. Bryson A.E., Denham W.F.A steepest-ascent method for solving optimum programming problems. J. Appl. Mech. (1962), pp. 247-257.
https://cimg1.ibsrv.net/gimg/pprune.org-vbulletin/1336x430/screen_shot_2021_02_16_at_8_47_09_pm_61846e1851960f72a11d646 1101e44afc966d793.png
https://cimg2.ibsrv.net/gimg/pprune.org-vbulletin/1460x908/screen_shot_2021_02_16_at_8_47_33_pm_efe34701a06bce6f5b00f3b 6c1601810cfcb474b.png
Salute!
Outstanding, FDR.
I resigned when the Block 15 was meanest mother in the valley, and it was the most produced best I can tell.
At flighthappens.....
Quote:
Originally Posted by fdr View Post (https://www.pprune.org/military-aviation/638681-thrust-vectoring-effect-rate-turn-2.html#post10991941)
Up in area where 3D maneuver is possible, each driver is trying to get out of plane with the other at the cost of energy loss. The start will have reasonable energy, and altitude permits recovery of energy loss from a bout of TV...
Based on what?
Well based on actual encounters in several conflicts going back to when TopGun school came about and USAF upgraded their Weapons School training. Poof! We got two aces in 1972 before the war ended and turned the stats around. Then look at Desert Storm and Falklands and... and...
The main reason we wanted high E entering an engagememt was as FDR described. Yeah, my turn radius big, rate low, but if I am zooming up and he cannot match that, I can come back down and get my E back with another gee from God. Go see a Raptor demo.
Secondly, thanks to FDR for the graphics graphic.... I want all here to look at the Viper E-M graphic concerning rates, gees and energy. Note that we could maintain over 8 gees until running outta gas using max power and at 380 to 400 knots. For the bat turn, 350 knots better, but not good unless bandit already slow and floundering. Look at the obscene turn rates. Note we could have excess energy and climb while pulling 4 or 5 gees. Gotta tellya, first time others engaged they were impressed. That was us 40 years ago. At the Lossiemouth Bomp Comp back in early 80's, our team shot down 80 bandits upon ingress and exit while only losing one.
...Gums sends..
Pugilistic Animus
17th Feb 2021, 14:57
Fascinating to look at the detailed nuts and bolts of thrust vectoring. As an aside, I used to HATE linear algebra class and I only got a B, but now I use it all the time...I should go back to school and take it again for an A :}
Pugilistic Animus
18th Feb 2021, 05:09
Just one more thing, those matrices and all of those graphs were probably drawn by a female human computer. The sloppy looking integration was most likely written out by engineers.
Deskscribbler
18th Feb 2021, 11:30
One other way to think of the Sukhoi/F22 etc. TVC is by drawing a vector diagram.
To pitch the nose up, the donks alter their axis of thrust giving a vertical component. Say, a 20 degree offset. Take an F22 at altitude producing 50,000lb combined thrust, that gives a vertical component of thrust (down) of about 17,000 lb which is countering lift, so is an extra "weight" to be borne by the wings. As far as the wings are concerned, the aicraft suddenly "weighs" 17,000 lb more.
50,000 lb gross weight, at corner velocity pulling 9G the airframe was producing 450,000 lb of lift. Add in TVC and it is now being asked to produce 467,000 lb of lift so something has to give - either G has to reduce (reducing turn rate) or the plane has to accelerate to produce the extra lift (also reducing turn rate). (Both in steady state, suddenly chucking in TVC would probably bend things!).
TVC also offloads the tail aero surfaces, reducing their trim drag and downforce... so it may end up all just cancelling out.
That's what thinking back to my Aero Eng tells me anyway!
Salute!
Great point, Desk.
From watching the F-22 demos, seems the best use of the nozzles is at very slow speed and high AoA condiitons, not at corner velocity.
The new F-35 puts on an eye-watering demo and does not use TV, just great aero and a humongous motor.
''Gums sends...
ex-fast-jets
18th Feb 2021, 19:29
I used Thrust Vectoring in the Harrier - and it did make the nose do some amazing things.
Some of them were what I wanted, to get a quick shot off, but the loss of energy was a problem.
Many of them were way different from what I wanted, and a "loss of control"- or something close - was often the sequel..........
Probably due to my incompetence.............
I don't know if MOG or anyone else actually utilised Harrier Thrust Vectoring in '82 in the air-to air environment - I suspect not as it was a relatively benign environment.
I used it over Stanley for different reasons in '82, but it's use did not achieve the end results that we were looking for!!
The charts and graphs on preceding posts probably explain why it often didn't work for me - clearly I spent too much time looking out of the window, and not enough time confirming that I was meeting all the parameters to achieve the correct variables that would have made my life so much better.
Salute!
LOL, ex-fast...
You got it.
Back in early days of the Viper we also looked around and not at some EM display we had that nobody could figure except the test pilot that got it on our selection of displays. We soon traded that display's "bytes" for something else, and the Norwegians needed bytes for the Penguin.
What we had going for us was we could pull and yank and bank and 90% of the time we would not depart and the plane was giving us best we could ask of it. You knew you were losing E when the gees went down and you were at an obscene AoA and couldn't move the nose.
... Gums sends...
Mogwi
19th Feb 2021, 09:32
I don't know if MOG or anyone else actually utilised Harrier Thrust Vectoring in '82 in the air-to air environment - I suspect not as it was a relatively benign environment.
Correct! Most engagements were in-shoot-away home for tea. I think that I was the only one to use VIFF in combat and that was trying to splash a Pucara in Stanley harbour.
Stanley was protected by a Roland missile system with the ability to get you up to 14,500' but I thought that it might improve morale if I could splash this guy who was stooging around at low level, in front of the Upland Goose. I left my #2 at 25,000', avoiding the odd 35mm burst and entered a steep dive with full power, in the braking stop to stabilise my speed around 250kts. This gave me a fairly stable platform to boresight the Pucara and get a 9L lock. First dive - no lock, recovered at 16k. Second dive - good lock but he would have crashed into the cathedral (not good for morale!), recovered at 17k. Final attempt - good growl but only intermittent lock, so pressed on a bit too long and ended up well below 14k at 250 kts with 2 x Roland heading for my arse!
I pulled the nose up, slammed the nozzles aft, tripped the water and stood on 21,500lbs of thrust, feeling silly and watching the missiles tracking me beautifully. Luckily made it to14,500' just before the missiles and watched them fall away a few hundred feet below me!
Sometimes seems like yesterday!
Mog
Odanrot
19th Feb 2021, 10:31
Just read that bit in your book - a bloody good read, so thank you, not only for helping me pass time in lockdown, but for what you and the boys did nearly 40 years ago.
Mog; your welcome to the Pucara crew probably would have been less enthusiastically received by the Pucara crew.
Would have been interesting to see how a forward cold nozzle only deflection, would have worked on the Harrier. that would seem to act to reduce long stab which would be helpful for getting rates for a modicum of thrust loss. Would be fun unless it was overcooked.
the graphs below (or the differences at least) predate even the Harrier, (R.I.P.) At VNE, the Venetian blind loses half its V in 6 seconds of turn, Tommy's plane losses that in 15 seconds from the analysis. Cheating is winning, whatever the ride.
Flew a couple of times with Al Curtiss pre 82, sad end.
https://cimg1.ibsrv.net/gimg/pprune.org-vbulletin/1148x1052/screen_shot_2021_02_19_at_5_22_37_pm_293636de98ca0addcc99f6e 74832afb00ee7442e.png
https://cimg2.ibsrv.net/gimg/pprune.org-vbulletin/1048x1042/screen_shot_2021_02_19_at_8_27_42_pm_a144fad2e5e8b2969ab2447 abc42c89ed1abdad9.png
Mogwi
19th Feb 2021, 12:20
Just read that bit in your book - a bloody good read, so thank you, not only for helping me pass time in lockdown, but for what you and the boys did nearly 40 years ago.
You are most welcome, Sir!
The book is about to be released in Argentina - could be interesting! Also being released in UK as an audiobook next week, for those who can't be bothered to read it!!
Mog