Acceleration

[garrya]

So i was reading the article posted here
viewtopic.php?f=55&t=27253&start=60
one thing that strikes me as odd is when pilot talks about acceleration of F-35

-Since I can slow down fast I can point my plane at my enemy for longer before the roles are reversed. The backside is that you loose energy, but it's not really a problem. The plane has so much engine power and low drag that the acceleration is awesome. With a F-16 I would have had to dive to gain as much speed after a hard turn.

Basically , he implied that F-35 accelerate much better than F-16 ( which i think could well be true at subsonic speed). Then there is also this



. But then i also saw another old chart today , and it abit weird because according to the chart , even the fastest version of F-35 still accelerate slower than F-16 , even at dogfight speed

So which is true then ???

[count_to_10]

Could he be talking about an F-16 with weapons and tanks, and maybe at a higher fuel fraction?
Or maybe the reported charts for the F-35 are performance degraded in some way.

[optimist]

I remember during early testing. The f-16 chase plane needed to hit the burner, to keep up with the f-35 during it's non burner acceleration.

[steve2267]

I remember during early testing. The f-16 chase plane needed to hit the burner, to keep up with the f-35 during it's non burner acceleration.

There's a video around where LM Chief Test Pilot Beesley remarks that F-16 chase needs to keep "tapping his burner" to keep up.

[steve2267]

I have been unable to find the video in which I recall Jon Beesley stating the F-16 chase plane needs to keep tapping burner just to keep up.

I am reminded that I have read that the F-35 possesses F-16 like acceleration and F-18 like maneuverability.

However, Google appears to be strong with me today:

F-35 Lightning II Flight Tests
15 June 2007 by Eric Hehs
<snip>
How has your impression of the F-35 changed in subsequent flights?

(Jon Beesley, then Lockheed Martin Chief Test Pilot for the F-35, replies)
"I continue to be impressed with the performance of the aircraft. The F-16s flying chase don't have near the fuel capacity or payload capability as the F-35. The Lightning II does very well in comparison. For example, the F-35 often forces the chase aircraft into afterburner when it is in military power.

The airplane's handling qualities continue to be very good throughout the flight envelope. When I raise the landing gear, the airplane flies very smoothly. The landing gear is sequenced, which is unique for a fighter. The nose gear comes up first, then the main gear follows. The gears drop down in reverse order. Another strong impression is that the airplane wants to fly a lot faster than we are allowed to fly at this point in the flight test program. Most of the time we fly at about thirty to forty percent of available thrust. This airplane can go out to high subsonic speeds very easily without using afterburner."
<snip>
Source:http://www.codeonemagazine.com/f35_article.html?item_id=33

Flying The F-35: An Interview With Jon Beesley, F-35 Chief Test Pilot
September 10, 2010 Author not listed
<snip>
"The acceleration of the aircraft in the subsonic envelope is very similar to the acceleration performance of an F-16 with a centerline tank on board. Often in chase situations the F-16 chase aircraft will need to select afterburner during the climb. The most impressive part of this is the performance of the F-35 with full internal weapons (two 2000-pound JDAMs; 2 AIM 120s) is changed very little."
<snip>
Source:http://www.dailyairforce.com/234/flying-the-f35-an-interview-with-jon-beesley-f35-chief-test-pilot/

Google-fu of "f-35 f-16 frontal comparison" and clicking on [ Images ] from the Google results led me to a few graphics from other f-16.net threads:

F-35 & F-16 (Block 50 +) - Comparison of frontal view. (viewtopic.php?f=55&t=15061&)hilit=frontal+profile


and



With a little imagination, I think, to a first order estimate anyway, the x-section area of an F-35 is on the order of the x-section area of a clean F-16 (no missiles, no wing drop tanks) with a centerline tank, a configuration to which Beesley referred above.

However, if this graphic scales all aircraft correctly,from the thread Frontal profile comparisons - F-35 vs other jets (viewtopic.php?t=18478)


the F-35 would appear to have a greater cross-sectional (frontal) area than an F-16 with a centerline droptank, which to me, makes the F-35 performance even more impressive.

Lastly, here is an interview with U.S. Air Force test pilot Lt. Col. Hank “Hog” Griffiths:

Latest From F-35 Tests
8/20/2010 by Guy Norris
<snip>
"Even when loaded internally with two 2,000lb GBU-31 Joint Direct Attack Munitions and two AIM-120 AMRAAMs, Griffith says the sheer power of the Pratt & Whitney F135 is evident. “The engine has a lot of thrust. It’s been fun to outrun the F-16 (chase aircraft). They can’t keep up. If we go to full military power the F-16 has to go to afterburner to keep up.”
<snip>
Source: https://justinwrites.wordpress.com/2010 ... -35-tests/

From the thread What's the F-35's VCS compared to other aircraft (viewtopic.php?f=22&t=41954 )


So, to the original question, I do not see a conflict between the two graphics posted. With regard to the first graphic, where pilots were comparing F-35 performance to other aircraft they had flown, a combat configured F-16C will have a minimum of two wing tanks, plus at least two AIM-120s, and possibly a Lantirn or other sensor pod, and another couple bombs. I think it is clear that an F-35 will regain airspeed (i.e. out-accelerate) an F-16C in that configuration.

As to the second graphic, that is saying that a stripped F-16 with no missiles and no tanks will accelerate slightly faster than an F-35. The pilot quotes I found all stated that the F-16 chase planes all had to keep tapping burner to keep up with the F-35. Typically these chase planes have no missiles (it's a flight test, not a combat or combat training sortie) and either two wing tanks or a single centerline tank. Beesley specifically compared the F-35 acceleration to being like an F-16 with a single centerline tank. I would expect an F16 with a single centerline tank (e.g. an F-35 per Beesley) to accelerate faster than a viper with two bags on the wings, but be slightly slower than an F-16 without any tanks.

In summary, without hard numbers / flight test data, all anecdotal evidence in the form of pilot quotes / interviews points to the F-35 having F-16 like acceleration. (Which is nothing to sneeze at.)

[playloud]

I spoke to an F-35 pilot at Nellis the other day during the airshow. He was a former Viper pilot. He said he has out-accelerated an F-16 that was carrying nothing but a centerline tank (both planes flying the say speed, and got into full burner at the same time). He said if the F-16 was completely clean, he believes the acceleration would be very similar to the F-35.

Edit: This also jives with the bar graph above.

[steve2267]

New Fighter Jet: Controversial Future of the U.S. Fleet
David Majumbar November 7, 2008
<snip>
In terms of aerodynamic performance, the F-35 is an excellent machine, Beesley said. Having previously been only
the second man ever to have flown the F-22 Raptor, Beesley became the first pilot ever to fly the F-35 in late 2006.
As such, Beesley is intimately familiar with both programs. According to Beesley, the four current test pilots for F-35
have been most impressed by the aircraft's thrust and acceleration. In the subsonic flight regime, the F-35 very
nearly matches the performance of its' larger, more powerful cousin, the F-22 Raptor, Beesley explained. The
"subsonic acceleration is about as good as a clean Block 50 F-16 or a Raptor- which is about as good as you can
get." Beesley said.
<snip>
Source:http://www.livescience.com/3032-fighter-jet-controversial-future-fleet.html

livescience.com-New Fighter Jet Controversial Future of the US Fleet.pdf

(89.83 KiB) Downloaded 7177 times

An oldie but a goodie quote. Found this perusing some other threads. Article previously linked by (at least) spaz.

Note date of article is 2008. The context of the quote then is from early in the flight test phase (SDD?), so I assume Beesley's comment at this time would be for performance of an F-35A without weapons loaded. If so, then unloaded F-35A accelerates like clean F-16 Block 50. If not, and this comment came from Beesley flying an F-35A with a full internal load (2xAIM120 + 2x2000lb bombs), then that would be even more impressive. Reading between all sorts of lines, it seems like unloaded F-35A <> clean F-16 Block 50, and loaded F-35A <> F-16 Block 50 with single centerline tank. Still nothing to sneeze at.

Put this post in the FWIW file. (Probably not much).

[blindpilot]

Interesting conversation here, but I would add one note of caution. Aeronautical cross section is not the same as a frontal slice view, or even RCS related cross section.

Consider a heavily area ruled fighter like the F-105. Because of the well designed "wasp waist" the visual wing and tail section pieces on the frontal cutout view actually do not exist as an aero cross section. The fuselage is pinched at that point to be exactly less cross section added by those elements, maintaining the constant cross section flow of the leading nose cross section.

Even this varies by speed, wing loading, AoA and weight (induced drag).

Not only are the pretty black card board frontal cross section views less than fully useful, they can be misleading. At best these pictures give us a general relative size comparison, which may not translate to drag directly.

Just saying.

BP

[steve2267]

Interesting conversation here, but I would add one note of caution. Aeronautical cross section is not the same as a frontal slice view, or even RCS related cross section.

Consider a heavily area ruled fighter like the F-105. Because of the well designed "wasp waist" the visual wing and tail section pieces on the frontal cutout view actually do not exist as an aero cross section. The fuselage is pinched at that point to be exactly less cross section added by those elements, maintaining the constant cross section flow of the leading nose cross section.

Even this varies by speed, wing loading, AoA and weight (induced drag).

Not only are the pretty black card board cross section views less than fully useful, they can be misleading. At best these pictures give us a general relative size comparison, which may not translate to drag directly.

Just saying.

BP

You make very good points, BP. I was being lazy and just threw up some images I could quickly find to try to illustrate an approximate frontal view comparison between the F-16 and the F-35. If I hadn't been so lazy, I would have photocropped the images to just show the F-35 and F-16.

In a way, though, the cardboard cutout image highlights your point. IF the cardboard cutout image is to scale... how much more impressive the F-35 acceleration performance is, if it compares favorably to the F-16. The F-35 would seem to have a much larger cross-sectional area and would therefore "seem" to have to be a LOT draggier. Bigger engine aside, the aero guys seem to have worked some real magic to minimize transonic drag on the F-35. I think sgtmac even noted this when he stated (somewhere here on F-16.net) that the F-35 appears to have been carefully area ruled as he noted that when "one bump" was diminishing, another "bump" began to grow.

[smsgtmac]

New Fighter Jet: Controversial Future of the U.S. Fleet
David Majumbar November 7, 2008
<snip>
In terms of aerodynamic performance, the F-35 is an excellent machine, Beesley said. Having previously been only
the second man ever to have flown the F-22 Raptor, Beesley became the first pilot ever to fly the F-35 in late 2006.
As such, Beesley is intimately familiar with both programs. According to Beesley, the four current test pilots for F-35
have been most impressed by the aircraft's thrust and acceleration. In the subsonic flight regime, the F-35 very
nearly matches the performance of its' larger, more powerful cousin, the F-22 Raptor, Beesley explained. The
"subsonic acceleration is about as good as a clean Block 50 F-16 or a Raptor- which is about as good as you can
get." Beesley said.
<snip>
Source:http://www.livescience.com/3032-fighter-jet-controversial-future-fleet.html

livescience.com-New Fighter Jet Controversial Future of the US Fleet.pdf

An oldie but a goodie quote. Found this perusing some other threads. Article previously linked by (at least) spaz.
...

Keep in mind today’s F-35A is more than a half a ton lighter than the aircraft Beesley described as having sub-sonic acceleration on par with the Raptor. In 2008, the “non-weight optimized” AA-1 was the only bird flying.
(http://www.dote.osd.mil/pub/reports/FY2 ... Report.pdf)

Estimates at the time of the SWAT effort were that in driving out the excess weight as needed for the F-35B, the “other variants” would lose about 1300 lbs as well.
http://www.airspacemag.com/military-avi ... 17183/?all

The last DOT&E report that talked about F-35A weight changes characterized the F-35A objective weight target NTE weight baseline aircraft as AF-72. All that come afterwards (until more goodies earn their way past the weight police) should be almost exactly the same weight. From FY14 DOT&E Report Pg. 46:

Weight management of the F-35A is important for meeting air vehicle performance requirements and structural life expectations. These estimates are based on measured weights of components and subassemblies, calculated weights from approved design drawings released for build, and estimated weights of remaining components. These estimates are used to predict the weight of the first Lot 7 F-35A aircraft (AF-72), planned for delivery in August 2015, which will be the basis for evaluating contract specification compliance for aircraft weight.
- According to these reports, the program has reduced weight by 16 pounds in CY14 (from January to October estimate). The current estimate of 29,016 pounds is 355 pounds (1.2 percent) below the planned not-to-exceed weight of 29,371 pounds.
- The program has demonstrated positive weight management of the F-35A over the past 38 months, showing a net loss of 123 pounds in the estimates from August 2011 to October 2014. The program will need to ensure the actual aircraft weight meets predictions, as well as continue rigorous management of the actual aircraft weight beyond the technical performance measurements of contract specification in CY15 through the balance of SDD to avoid performance degradation that would affect operational capability. (

http://www.dote.osd.mil/pub/reports/fy2014/pdf/dod/2014f35jsf.pdf)

[blindpilot]

Interesting conversation here, but I would add one note of caution. Aeronautical cross section is not the same as a frontal slice view, or even RCS related cross section.

... At best these pictures give us a general relative size comparison, which may not translate to drag directly.

Just saying.

BP

You make very good points, BP. I was being lazy and just threw up some images I could quickly find to try to illustrate an approximate frontal view comparison between the F-16 and the F-35. If I hadn't been so lazy, I would have photocropped the images to just show the F-35 and F-16.

In a way, though, the cardboard cutout image highlights your point. IF the cardboard cutout image is to scale... how much more impressive the F-35 acceleration performance is, if it compares favorably to the F-16. ...

Indeed the design (heavily computer aided) is impressive.

Full disclosure - my aero degree is in structures (breaking things and materials) and not fluid dynamics beyond aero 101 stuff, so take my comment with the appropriate allowances.

BP

[steve2267]

I attended a pilot "talk" given by an F-22 / F-15 driver. (This was something through the FAA Wings program, if memory serves.) Two things stuck in my head. One, as an F-22 pilot, flying against the F-15 was like "clubbing baby seals." The second may not be attributable to him, but to an F-117 pilot quote -- I can't recall -- but the sentiment was that given the choice between being invisible or being super-maneuverable, the pilot chose invisibility, every time.

Take an F-16, stir in a little A-7, bake, then sprinkle on a generous helping of F-117. What do you get? An F-35.

[count_to_10]

I attended a pilot "talk" given by an F-22 / F-15 driver. (This was something through the FAA Wings program, if memory serves.) Two things stuck in my head. One, as an F-22 pilot, flying against the F-15 was like "clubbing baby seals." The second may not be attributable to him, but to an F-117 pilot quote -- I can't recall -- but the sentiment was that given the choice between being invisible or being super-maneuverable, the pilot chose invisibility, every time.

Take an F-16, stir in a little A-7, bake, then sprinkle on a generous helping of F-117. What do you get? An F-35.

Your missing quite possibly the most important part: the sensor fusion on the F-35 makes the pilots the next best thing to omniscient. So what do you add in to represent that?

[steve2267]

I attended a pilot "talk" given by an F-22 / F-15 driver. (This was something through the FAA Wings program, if memory serves.) Two things stuck in my head. One, as an F-22 pilot, flying against the F-15 was like "clubbing baby seals." The second may not be attributable to him, but to an F-117 pilot quote -- I can't recall -- but the sentiment was that given the choice between being invisible or being super-maneuverable, the pilot chose invisibility, every time.

Take an F-16, stir in a little A-7, bake, then sprinkle on a generous helping of F-117. What do you get? An F-35.

Your missing quite possibly the most important part: the sensor fusion on the F-35 makes the pilots the next best thing to omniscient. So what do you add in to represent that?

X-wing.

I tried to argue in the nickname thread that the F-35 should be called the X-wing. I mean, if you're going to be master of the Jedi Transition, ruler of Star Wars Canyon... you might as well grab the name while it is open.

May the Force be with you.

[playloud]

Adding a Stubby vs Rhino comparison.