"Aircraft acceleration" Topic

Suppose an a/c is in level flight and not turning/rolling etc.

The pilot opens up the throttle and possibly engages a water-methanol or similar boost.

How much acceleration is he going to get?

I know it depends on a host of variables but what is the range of possibilities.

I'm looking for answers in m/s/s or similar and for specific types of ww2 aircraft.

I've been googling but nothing is popping up right away.

Have a look for 'specific excess power'.

Depends on what speed he's going already. If the drag force is already very high, the extra force from the boosted engine is not going to produce a very high resultant acceleration.

Ok – let's suppose the a/c is at cruising speed and fairly high – 15-25,000 feet up.

He has no extra drag from drop tanks or ordnance and he engages all the extra power he can to accelerate. How much acceleration are we talking about??

The only figure I've got so far is modern jet airliners accelerate at 2-3m/s/s when taking off – though they could do more if needed and the passengers wouldn't be 'inconvenienced'.

I'm looking into 'specific excess power' so thanks for that lead.

I would post on a forum that a reputable WWII miniature rules writer frequents.

Maybe Check Your 6 (Scott Fisher) or Whistling Death (J.D. Webster)

Good Luck

OK – will try that..thanks.

An upper bound for the acceleration can be guesstimated from modern jets which have thrust-to-weight ratios of around 1.0, i.e. they can counteract the acceleration due to gravity if they point straight up, which means they can accelerate at around 1g or around 10m/s/s. Considering that WW2 aircraft performance won't be as good as this and they will already be travelling at some speed, how about an upper bound of 5m/s/s? So I think Skarper's answer of 2-3m/s/s is about right.

I've been picking up a few figures here and there.

Apparently a Mig 29 can accelerate at 10.4 m/s/s during take off (albeit in an airshow configuration)

And I have a number of comparisons of WW2 fighters from this site

link

that seem to give acceleration figures that look like bing in the range of 5-7 m/s/s – though no idea where these came from. The do seem reasonable however.

Modern jet fighters have far more power but are also far heavier than ww2 a/c – so I think I'm in the right general area.

Of course – it depends how fast the aircraft is already flying and how high it is – plus extra drag would really reduce acceleration.

Very difficult data to find.

I suspect in many cases that you'd need to check individual aircraft spec data, one at a time, though you might get lucky and someone has already done the work.

Much easier to determine/calculate are horsepower to weight ratios, so you might try looking at that data, if you can get a baseline for at least one aircraft.

Of course, that doesn't include aircraft drag, the speed at which you start, etc., but is a reasonably good baseline for comparing aircraft.

To further complicate things, aircraft all have different power curves, and altitudes at which they are better/worse than one another, but that's another issue to consider.

Finally, German jet engines in WWII were slow to accelerate when compared to props, at low speeds, but once they got going they were pretty efficient, as long as they were kept near full thrust.

Yep – pretty much searching for the key one or two a/c to extrapolate from.

I think within my game I'd only have two categories – high and normal power with low power existing but not represented. I've worked out more or less how much speed to lose/gain for climbing and diving and don't want the extra speed gained from full power to be out of step with this.

My turns are only 3 seconds long and speed ranges in 120km/h chunks from 2 [almost stalling] to 7 for a diving P-47 [Komets and Me262 are faster at 8 and 9 if diving]

If I allow full power to increase speed by one it makes for an 11m/s/s rate of acceleration. Which I'm thinking is too much.

I think to gain any speed from full power use an aircraft would have to not be turning or rolling or climbing. I assume any specific excess power would be mostly used up countering the extra drag or gravity.

I supposed this information would have been necessary for any WW2 air combat game so there would at least be a list of stats to crib. But it seems to be an area where data is lacking and the tests not fully comparable.

Appreciate all the help so far and more would be a bonus.

Your best bet might be to inquire with a present day air-racer, here in the USA, using WWII airplanes, and ask them.

I suspect they may be able to get you in the ballpark.

Make sure to inquire about stock performance, and not the overblown, super-charger models they're using. Still a few P-51s racing, last time I checked, in addition to the Sea Fury's and others.

If I had to take a stab at it, I would imagine it might take about a full minute, or so, from a standing start/stalled, to get up to full speed. Possibly more.

I also always presumed that prop planes could accelerate about twice as fast as a jet (WWII) at the low end of the power curve band, but that probably changes as the speed of the jet increases.