Most Favorable Conditions

Hello!

I’m taking the flying whale out for a test flight. I’ll be flying at 100 feet on a flight from Los Angeles to Sydney on solo. I was today years old when I learned that something as small as temperature can affect the airspeed of the plane. So, what would be the most favorable conditions for me to have to break the sound barrier and maintain the speed of sound?

Thanks!

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rn I’m averaging M0.95 at 725 knots ground speed. Current temperature is 12 degrees celsius with 98 knot tailwinds.

M 0.95 is too fast. M 0.85 is the ideal speed.

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Uhhh… The whole point of this experiment is to exceed Mach 1.

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My apologies. I saw the stall signal and thought that was the issue.

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Ah, no worries

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The higher you are, the faster you go, however this is limited by engine thrust

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I want to stay at 100 ft for this experiment. If I were to climb, what would be the ideal altitude, temperature, load, and windspeed?

So this is why IF will never add Concorde. I’m at M0.95 on solo and it’s already hella laggy.

You could always just put the wind up to the maximum as well.

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Your airspeed shows 661 knots (at your zero VS with full throttle). 661 knots is 771 mph which is, magically(?!) the speed of sound at sea level at a temperature of 15 degrees C (59 degrees F). You are exactly at the speed of sound, coincidentally(?) just so happens to be maintained at full throttle!(?)

Hopefully I don’t wake up tomorrow and find I made a mistake…

.Check out the first line of the table in the following link:

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After that I notice your HUD does indeed say M1.0, so that fits with the theoretical numbers.

At full throttle at higher altitudes, do you get the M1.0 airspeeds as shown in the table I wonder?

If the flight model saturates the full throttle airspeed at the theoretical speed of sound for each altitude as shown in the chart, it implies the only way you could go faster is to dive somewhat at full throttle.

But that’s not sustainable for your cruise flight to Sydney.

Good luck with you flight!

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Already did

This was after a 5000 foot descent.

Which plane would be able to maintain M1.0?

Looking at your HUD again, your gs is less than your airspeed with nearly a 100kt tail wind?! Correct me if I’m wrong but isn’t your OAT -90c (hard for me to read), rather than 12c?

Doesn’t make sense, you’re close to sea level and recording the world’s record-breaking low temperature!! Ah ha, solo mode, where you can set temperature manually.

The bar slides all the way down to -90c, which is a record breaking low sea level temp?

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Yes?

(edit: after writing this I tried several aircraft at max temp, got the good higher gs but speed of sound went up enough to keep me at M number similar to yours, less than 1.0 - can’t win?)

So the colder your air, the more IAS reads above TAS. TAS is the relevant speed for speed of sound in air.

The problem is the speed of sound changes with temp also. I wonder what the speed of sound is at -90C?

If you want the fastest possible GS of course max out the tail wind.

As @Panther mentioned, “The higher you are, the faster you go, however this is limited by engine thrust” because it gets you the fastest TAS for your IAS.

So for in terms of temp that would translate into wanting the highest “density altitude” you can get away with. For high density altitude you want it as hot as possible rather than cold. Thins the air so the aircraft needs to be moving faster through the air to look like the same pressure over the surfaces.

As for which subsonic aircraft has the best engines to do this, someone else I’m sure knows more about this than me.

Good luck, I’ll be listening for your sonic boom!

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Higher outside temp will result in lower airspeed in IF.

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I think we agree?: hotter gives lower IAS for a given ground speed (assuming no wind). It’s consistent with density altitude precautions for mountain flying. On a hot day, you may not get enough airspeed to clear the trees; your take off requires a higher ground speed.

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