Forum: F-16 Simulators

Hello everyone, this is my first post here. I have been playing falcon [Link pending approval] for about a month or 2 now and I'm curious about the realism on one point. From what I've read about the f-16 it can accelerate vertically? This means that at 90 degrees straight up it can not only maintain speed but gain speed as well?

In falcon [Link pending approval] I've been trying to do this. I'll go to full afterburner and fly level until about 500 knots and then pull to 90 degrees straight up. But it will just slow down really fast until it stalls if I leave it there. I've tried it with no weapons, external tanks or anything on the plane with only about 1000 pounds of fuel and it still loses speed. Is this how a real F-16 handles or is it a simulator thing?

F-16.net Sponsor

The only thing that'll keep accelerating vertically is a rocket. And jets aren't rockets (although some jets have aspirations to be such...see the F-104 Wink

). Jets like the Viper and the Eagle will climb in the vertical like scalded dogs but they won't zoom into orbit. They'll eventually sputter out the longer they stay vertical as the decrease in net thrust at the higher altitudes (I mean like...WAY up there) can't overcome the jet's weight, even after burning off the gas it took to get there. So they eventually have to push over and start behaving like a airplane again.

I remember trying to do the same some time [Link pending approval] it at low altitude, since the engines thrust decreases with altitude.
If you fly level at a couple of hundred feet, the pull up vertical you'll be able to accelerate vertically, but only for a short time, then speed will begin do decrease.

As above - also maybe worth defining if they actually mean 90 degrees straight up and the block type in the text you were reading.

The F-16C Block 30/40/50/52 have more powerful 28k thrust engines.

Elite 1K Joined: May 26, 2005 - 08:39 PM Posts: 1496

Yep, altitude has a lot to do with it. At sea level and 500 knots if you're making 28k pounds of thrust, you'll be making 21k pounds at 10,000 feet at the same speed and only 15k pounds at 20,000 feet. At 35,000 feet you're not even getting 10k pounds of thrust.

Well, here's what people don't realize: a better than 1:1 T/W ratio does not mean you can accelerate vertically. Thrust must be greater than Weight + Drag. Drag is SUBSTANTIAL at the airspeeds where jet engines perform best (ie 400 knots, not 0 knots).

Additionally, the airspeed you see in the HUD is indicated (or calibrated)airspeed, not true. A constant true airspeed (think actual velecity) will look like decreasing calibrated airspeed as you climb.

So, to see if you're actually accelerating vertically you need True Airspeed, and Thrust > Weight + Drag.

I know of no fighter that can actually do this. Even if one could, it would only be for a couple seconds as engine thrust decreases dramatically with altitude.

Last edited by johnwill on Jan 30, 2011 - 08:08 AM; edited 1 time in total

sea0fgreen.

When in your vertical climb, what speed indication are you using? Indicated airspeed? Mach number? Neither of those can tell you how much you are accelerating or decelerating. To do that, you must monitor True Air Speed. Why? True airspeed is how fast you are moving through the air, indicated airspeed is the pressure you would feel if you stuck your hand outside (don't try this, kids), and mach number is how fast you are going relative top the speed of sound at your speed and altitude. In your vertical climb, at constant TAS (constant velocity), as your altitude increases, IAS will decrease and mach number will increase. Above a certain altitude, mach will stay constant, but let's neglect that for this simple example.

Let's say you are at 500 kt (IAS and TAS) at sea level, which is 0.756 mach. Pull up to a 90 degree climb and adjust thrust to maintain 500 kt TAS. Don't worry, in this example, you have unlimited thrust. As you pass 10,000 ft, IAS is 439 and mach is 0.783. At 20,000, IAS is 380 and mach is 0.814. At 30,000, IAS is 324 and mach is 0.848. Struggling up to 40,000, IAS is 267 and mach is 0.872. Remember TAS, your actual speed, is still constant at 500 kt.

So what's the point? The point is, you can be accelerating (TAS increasing) and your indicated airspeed can be decreasing. Say at 10,000 ft, your IAS has decreased from 500 kt to 484 kt. Have you slowed down? No, in fact you have accelerated from 500 TAS to 550 TAS.

So, go back and try your vertical climb again, this time monitoring TAS. If Falcon 4 doesn't give you TAS, then compare with the IAS speeds i gave you above.

Well, I see flyboy22 has posted similar information. He is totally correct.

I'd agree with the IAS/TAS explination, but will address this.

flighthawk wrote:

The F-16C Block 30/40/50/52 have more powerful 28k thrust engines.

One not only has to consider 'the more powerful thrust engines', but the dry weight of the aircraft in question.

A Block 15 A model with a PW-200 could have better T/W performance than a Block 40 with a more powerful engine.

The C models have a higher dry weight, and the GE engines, and PW-229 do weigh more than the PW-200.

The highest T/W ratio of the whole series is the Block 42s that have been upgraded to PW-229 engines (Of the Block 52 variety)

So even though the Block 42 w/PW-229 has the same 'IPE' engine as a Block 52, the airframe is lighter.

Likewise the Block 40 w/GE-100, is a heavier airframe (with a heavier engine) than the Block 15 w/PW-200

Food for thought Cheers

TEG

That_Engine_Guy wrote:

I'd agree with the IAS/TAS explination, but will address this.

flighthawk wrote:

The F-16C Block 30/40/50/52 have more powerful 28k thrust engines.

One not only has to consider 'the more powerful thrust engines', but the dry weight of the aircraft in question.

A Block 15 A model with a PW-200 could have better T/W performance than a Block 40 with a more powerful engine.

The C models have a higher dry weight, and the GE engines, and PW-229 do weigh more than the PW-200.

The highest T/W ratio of the whole series is the Block 42s that have been upgraded to PW-229 engines (Of the Block 52 variety)

So even though the Block 42 w/PW-229 has the same 'IPE' engine as a Block 52, the airframe is lighter.

Likewise the Block 40 w/GE-100, is a heavier airframe (with a heavier engine) than the Block 15 w/PW-200

Food for thought Cheers

TEG

By default Falcon 4 AF only lets people fly the F-16AM MLU , and F-16C Block 30/32/40/42/50/52 and CCIPs of the 40/50s

wasnt aware the 42 had the bigger engine - dont think it did in the game - but anyway if he is using the F-16AM for example (empty weight similar to block 40?) - its acceleration really was useless compared to the block 30/40/50 in game.

According to our friends at J@ne'$

Here is some 'raw comparison data'

Weight empty:

F-16A 7,070 kg (15,586 lb)
F-16B 7,374 kg (16,258 lb)

Maximum weight for F-16A/B with external load 16,057 kg (35,400 lb)

Weight empty (Block 52/50)

F-16C: F100-PW-229: (Block 52)
with CFTs 9,358 kg (20,631 lb)
without CFTs 8,910 kg (19,643 lb)

F-16C: F110-GE-129: (Block 50)
with CFTs 9,466 kg (20,868 lb)
without CFTs 9,017 kg (19,880 lb)

F-16D: F100-PW-229 (Block 52)
with CFTs 9,760 kg (21,517 lb)
without CFTs 9,312 kg (20,529 lb)

F-16D: F110-GE-129: (Block 50)
with CFTs 9,867 kg (21,754 lb)
without CFTs 9,419 kg (20,766 lb)

Maximum weight for F-16C/D Block 50/52 with external load 21,772 kg (48,000 lb)

Now add into the equation the engine performance. (also raw data from J@ne'$)

F100-PW-220 1,481 kg (3,265 lb) @ MAX AB - 105.72 kN (23,770 lb st)
F100-PW-229 1,721 kg (3,795 lb) @ MAX AB - 129.45 kN (29,100 lb st)
F110-GE-100 1,778 kg (3,920 lb) @ MAX AB - 124.6 kN (28,000 lb st)
F110-GE-129 1,805 kg (3,980 lb) @ MAX AB - 129.0 kN (29,000 lb st)

So just looking at the engines. (Strictly engine T/W using figures above)
The PW-220 yeilds a T/W ratio of ~7.28/1
The GE-100 yeilds a T/W ratio of ~7.14/1

So just because a higher thrust engine is installed doesn't mean it will accelerate vertically any better than an older engine/airframe.

So you'd have roughly a T/W (at empty weight which is impossible to fly without fuel..)
A Block 50 with GE-129 ~ 1.45/1
A Block 15 with PW-220 ~ 1.52/1

Add 1000lbs of jet fuel and the figures would be lower but still favor the older Viper with the 'less-powerful' engine.

Air density would have A LOT of influence on engine performance as well. Temperature/Humidity greatly affect thrust, but for the conversation at had, all things would be equal if we were having a personal drag race at the same airfield.

As for the Block 42s w/PW-229s; that was a US ANG upgrade. Outside the ANG, nobody else has purchased new PW-229s to replace their older PW-220s. Unlike the upgrade 'kits' that could make the PW-200 into a PW-220; the PW-229 is so different a whole new engine is required. (@ $5 Million each) Block 42s don't weigh as much as Block 52s, and as such they enjoy one of the highest T/W ratios going. (From the official LM/PW figures I've seen) I can't imagine what a Block 32 or 25 would be like with 29K thrust, let alone a Block 15 or 20, A Model!

Keep 'em flyin' Thumb

TEG

in airshow performance, the F-16 show 90º acceleration, but is at low airspeed...

meanwhile you're climbing, the engine thurst decreased and the T/W ratio drop below 1

also the drag come a factor too...

and of sure, all the above explanations!

Appreciate what you are saying mr TEG - I had assumed (despite figures on this site) that the F-16AM MLU must be far heavier than the original F-16A Block 15 with the airframe and avionics upgrades to get it near the block40/50 standard.

In game figures were these - which must be near what the flight models are based on and explain why the MLU was a poor performer in game:

F-16AM MLU empty (no CFTs) 18,238lbs
F-16C Block 30 empty (no CFTs) 18,700lbs
F-16C Block 50 empty (no CFTs) 19,975lbs

I never thought about how the airspeed was displayed. Just tried it again. I was using a f-16C block 42, no weapons, TAS selected and only 700 pounds of fuel. I started at 200 feet altitude and 380 knots. I pulled up 70 degrees and there was a 1 or 2 knot increase before it started slowing down (it was almost 7000 feet by then). So there was some acceleration.

I was reading a description of the f-16 from a f-18 pilot on this site and he said the f-16 was capable of vertical acceleration. I don't know what that actually means though. I guess as long as your moving more vertical than horizontal. Anything above a 45 degree climb? I also seen the term used on a site describing a SU-27 for sale. The guy said it had a thrust to weight ratio of 1:1 which meant it could accelerate straight up. He was probably just a salesman though.

OK, glad you had TAS available for the correct indication of speed. You might try starting at other airspeeds (400, 500, ...) just to see the effect of increased thrust available and added aero drag.

As far as climb angle, vertical climb means 90 degrees or straight up. Anything less than 90 degrees reduces the effect of gravity along the flight path axis.

To see substantial acceleration, you'd probably need to start the simulator with the plane in full AB point up at 90 degrees. Falcon doesn't let you do this though. Most fighters today can accelerate vertically, there are just a lot of conditions that need to be met. I forget how much Falcon lets you change the weather, try to make it really cold, it will give you more thrust.

Forum: F-16 Simulators

falcon 4.0af accelerate vertically?