Forum: F-16 versus XYZ

yo,
im not exactly sure which one can pull it off....any help or opinions??

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I heard about some acceleration tests done by Lockheed earlier this year with a blk 50 frame installed with a blk 60 engine. static Takeoff to 30,000 ft was somewhere around 80 seconds. That's the best any F-16 can hope for. Not sure what it takes a clean eagle to get that high. I bet the E models get pretty close to the above figure.

Gums had mentioned it was unlikely, even though the rugged -15 had more thrust than weight due to many, many different factors. Accelerating is for the Raptor, climbing out in a slight deceleration is possible for quite some time. "A" and "B" models (-16) could not accelerate but during an FCF would gather enough kinetic energy prior to the 4 "G" pull up to FL200 it was very sluggish during the roll-out to upright was very obvious from observation.

Both the Eagle and the Viper can...but not right after takeoff Smile

A viper with nothing but internal fuel and the big GE engine can Accelerate in the vertical as long as it is above 200 kts, so in the time it takes to take off and retract gear, it can go vertical and accelerate, albeit at a very slow rate (`2-4 knts per second). "Big Mouth" vipers have a greater T/W than any Eagle, as -15Cs have the old less powerfull engines and while -15Es have the big engines they are vastly heavier due to the increase in structure.

A clean Viper during the engine test flight it takes off with full internal fuel load accelerates to 450knots at about 6000' from the start of the runway, pitches at about 70 degrees nose up ,accelerates to 510 knots!!!! and levels off at 20000' with 385 knots!!!!So?what do you think?

I don't know the specifics (numbers, etc.) but I would think one of our Eagles clean would give the Viper a run for it's money. Then again, we run
-220's in the back of our A models. Cool

We have a specific pilot who loves to pull max climbs for the simple reason of being too lazy to call the tower for clearance through the airport traffic when increasing altitude. He'll just call in a max climb to the tower and then yank the stick on take-off.

Elite 1K Joined: Aug 19, 2004 - 09:19 AM Posts: 1092

It's pretty difficult for most fighters to accelerate in the pure vertical for anything but a few short seconds. You hear all this stuff about a T/W ratio greater than 1:1, but those numbers are for A) uninstalled thrust of the engine and B) sea level static conditions. Although installed thrust of an F-16 or F-15 will actually increase beyond the uninstalled engine's sea level static (SLS) thrust rating as speed increased, so will drag. If you're interested in actual acceleration, you have to look at the (T-D)/W ratio at the current flight conditions and not just the theoretical T/W ratio of the clean jet with theoretical uninstalled SLS engine thrust rating. Anyway, once an aircraft pulls up into the vertical (90-degree pitch angle), it gains altitude VERY quickly... especially if it's already got a decent amount of airspeed to start with. This means that thrust will start to decrease rather quickly as well. So will drag, but not enough to offset the decrease in thrust with altitude. So you might get a second or less of actual acceleration after pulling into the pure vertical with an F-16 or F-15, but chances are you will reach a Mach number and altitude where your (T-D)/W ratio is below unity before your aircraft is actually established in a 90-degree pure vertical climb. Aircraft are usually decelerating in these vertical climbs.

As for the F-22 being able to accelerate in the pure vertical... perhaps for a few seconds given the right conditions, but it can't escape the decrease in thrust with altitude that all air-breathing engines encounter here on planet Earth. I guarantee that the F-22 doesn't have a (T-D)/W ratio above unity above 10,000 ft. and probably not even above 5,000 ft. That doesn't mean it won't climb like a bat out of hell, but the ability to accelerate vertically for any significant period of time is something you encounter with aircraft powered by air-breathing engines. You need a rocket that carries its own oxidizer for that kind of sustained power. Accelerating in the pure vertical is never really optimal anyway. You'll generally reach a given altitude faster in a less-than-90-degree climb, so pure vertical climbing capability isn't actually an true figure of merit anyway. Time to climb records are NEVER accomplished by trying to climb at anything close to a 90 degree climb angle. In fact, figuring out the 'path' of quickest ascent for a high performance aircraft like the F-15, F-16, or F-22 is a VERY complicating and involved series of calculations.

Good answer R1 Thumb

F-16 will accelerate verticaly to 10000ft. My Brother is a viper pilot.

Elite 1K Joined: Aug 19, 2004 - 09:19 AM Posts: 1092

Pilotasso wrote:

F-16 will accelerate verticaly to 10000ft. My Brother is a viper pilot.

Wow... really? Guess what... that doesn't mean you know what you're talking about. And no... it won't accelerate going STRAIGHT UP to 10,000 ft. I can prove this to you mathematically if you like. Tell me... what do you think the maximum thrust of an F-16 Block 50 is at 10,000 ft and, say, Mach 0.8? Guess what??? It's about the weight of the clean aircraft with full internal fuel load. Would you like me to calculate what the drag on the aircraft will be for various altitudes at Mach 0.8 up to 10,000 ft? Remember... (T-D)/W... if it's greater than 1.0 we have acceleration. If it's not, we don't.

Place your bets gentlemen... place your bets.

I place my bets with Isaac Newton and Jacob Bernoulli ... Smile

Raptor_One wrote:

Pilotasso wrote:

F-16 will accelerate verticaly to 10000ft. My Brother is a viper pilot.

Wow... really? Guess what... that doesn't mean you know what you're talking about. And no... it won't accelerate going STRAIGHT UP to 10,000 ft. I can prove this to you mathematically if you like. Tell me... what do you think the maximum thrust of an F-16 Block 50 is at 10,000 ft and, say, Mach 0.8? Guess what??? It's about the weight of the clean aircraft with full internal fuel load. Would you like me to calculate what the drag on the aircraft will be for various altitudes at Mach 0.8 up to 10,000 ft? Remember... (T-D)/W... if it's greater than 1.0 we have acceleration. If it's not, we don't.

Place your bets gentlemen... place your bets.

Ok let me clarify something. Your talking about mach 0.8 already, I was a bit too broad in my affirmation perhaps, but when you want to test if the plane can accelerate in vertical from 0 to 10000feet youll probably do it without pre-accelerating (horizontaly or climbing wich then you would waste a good deal of those 10000ft going anywhere but verticaly), rather start your vertical climb going straight from take off. Youll never reach mach 0.8 before getting to 10000ft and then your speed will drop. On the other hand your drag doing the climb in these conditions will be much smaller than in yours. Wink

Also if you fly a fast jet like this youll find out soon that 10000ft is not much youll get to it in few seconds anyway. Wink

Your mach 0.8 figure must have come from standard procedure to optimize climb for typical intercept altitudes wich are much higher in than only 10000ft and tipicaly you will have to ease your pitch angle to prevent from bleeding too much speed with altitude. Wink

Elite 1K Joined: Aug 19, 2004 - 09:19 AM Posts: 1092

Negative on that Pilotasso. I used Mach 0.8 because the INSTALLED T/W ratio at that speed is actually a reasonable amount higher than 1.0 for a block 50's gross weight at zero drag index with full internal fuel. If you want to start talking about the Mach 0.3-0.5 range you might be in if you pulled up into the vertical right after you retracted the gear, then you're dealing with an installed T/W ratio that is MAYBE just 1.0 at sea level and nowhere close to 1.0 at 10,000 ft. Installed thrust increases somewhat dramatically with airspeed. At low altitudes, it can easily exceed the uninstalled sea level static thrust rating of the engine itself if the aircraft is going fast enough. Mach 0.8 would be your best bet in my opinion to even come close to accelerating, if even for 1 second during the vertical climb. If you don't believe me, that's fine. You can get your brother on here and I will debate with him too.

You might be able to get a certain block F-16 to accelerate briefly in the vertical (not all the way up to 10,000 ft) if it was low on fuel and pulled up at just the right speed. Sometimes even pilots will say things about their jet's performance that they don't mean literally. They'll say accelerate into the vertical when they may just mean climb into the vertical without a noticeable loss of airspeed. In fact, the F-16 CAN go vertical without losing much airspeed at all in the 0-10,000 ft range... possibly even higher if it starts out with a good amount of smash. The pilot might even notice his Mach meter climb by 0.01-0.02 units. Since Mach number generally decreases with altitude, this isn't actually acceleration. I'd be surprised if an F-16 pilot actually switched to true airspeed during a vertical climbout to test whether his jet really accelerated. All the HUD videos I've seen show Calibrated airspeed. It's rare for pilots to use true airspeed for things like take-off and landing or maneuvering. For pure navigation... yes. Anything else... Calibrated.

Raptor_One wrote:

You might be able to get a certain block F-16 to accelerate briefly in the vertical (not all the way up to 10,000 ft) if it was low on fuel and pulled up at just the right speed. Sometimes even pilots will say things about their jet's performance that they don't mean literally. They'll say accelerate into the vertical when they may just mean climb into the vertical without a noticeable loss of airspeed. In fact, the F-16 CAN go vertical without losing much airspeed at all in the 0-10,000 ft range... possibly even higher if it starts out with a good amount of smash.

Perhaps this is the case, the affirmations I have been hearing from Af staff are a bit generic, yes. BTW the planes my brother talks are F-16A OCU and F-16MLU. Both with the same engine PW220E's. Respective weights are 16,285lbs empty (about +200lbs on the MLU)+internal fuel .

Forum: F-16 versus XYZ

F-16 versus F-15 accelerating in a vertical climb