Why can’t you fly as high & as fast with the planes in Infinite Flight as you can in real life?
I would like to illustrate this with the Boeing 737-700:
In Infinite Flight I can fly a maximum of 340 kts. or Mach 0.87 at a maximum altitude of 25100 ft. before the corresponding “Over Speed” warning sounds.
Then I looked up the real data for the 737-700, & found that the max speed is 0.82 (870 kts.), the cruise speed is 0.78 (830 kts.) & the service ceiling is 41,000 ft.
I have found such contradictory information on all aircraft types in the game.
Therefore, I request Infinite Flight team to revise maximum speed, service ceiling & cruise speed so that it is identical with actual data.
First of all, welcome to the Infinite Flight Community!
The cruising speed for the Boeing 737-700 is Mach 0.78, but the structural limit is much higher. To be on that limit doesn’t mean being realistic. If you set the speed to 295 knots, which then turns into Mach 0.78, you will be able to climb to higher, more realistc altidudes, in between 30,000 and 41,000 feet without getting any warning. There’s nothing wrong with the game, the limits are not suggestions on what’s the realistic speed.
Oh and that max speed (Mach 0.82) is not the airplane’s structural limit, it’s the highest sustainable cruise speed.
Under standard conditions (typical temperature etc.) at 40,000 feet, I found a value for the speed of sound = 660mph = 1062km/h
So for mach 0.82:
Mach speed limit = 0.82 x 1062km/h = 870 km/hr
So, your number of 870 is correct, but only if the units are in km/hr, as mentioned:
Also, the 870km/hr is the mach speed limit, and mach speeds are a measure of TAS (true air speed).
TAS is how fast the air is actually travelling past your aircraft.
The 340kts is IAS (indicated airspeed), not TAS.
IAS is the TAS corrected for pressure.
So, IAS is almost always lower than TAS because you are almost always flying in thinner air.
And, at an IAS of 340kts, you could easily be flying at TAS of 870km/hr (470kts).
IAS is important because it represents how much dynamic pressure the aircraft experiences over it’s wings, flaps, landing gear and other critical structures.
Not quite. The speed of sound varies with density which is a function of pressure and temperature. Mach is a function of TAS and the speed of sound. Put these together, and you get this: Mach is a function of TAS, pressure, and temperature. TAS is a function of IAS, pressure, and temperature.
TAS is the actual speed of the molecules of air moving relative to the aircraft.
TAS is not a function of anything. It is the actual speed of something relative to something else.
The mach speeds, as in the mach fraction numbers, are measures of TAS, or true speed of the air molecules relative to the aircraft, but in units of fraction of the local speed of sound.
And as you said, the local speed of sound varies dependent on local environmental conditions.
The mach number speed is TAS relative to whatever that local speed of sound is.
Safe conduction of flight requires speed in two measures, pressure speed, or IAS, and TAS (related to aerodynamic hazards near the speed of sound).
TAS is shown as a mach number because the hazards of TAS relate to molecules of air approaching the speed of sound relative to the aircraft.
edit: just to be clear, quite literally:
Mach number = TAS / speed of sound
so, again
Without making it too confusing the lower you are the faster you can go per se. The higher you get the slower you go - indicated.
At 10,000 a 76 can go over 340kts indicated, but at altitude(depending on weights, ISA, mountain waves… just to name a few factors ) and smooth air with decent payload is 250-270max. Also, max cruise on 76 is .86 and I have yet to do anything above .82.
Here’s a small picture illustrating this. I’ll try an take a pic above 10,000, below 18. You can see the GS and TAS displayed.
Love cockpit photos! So you’re
39,000ft
IAS 237kts
TAS 454kts
GS 448kts
M0.769
alt 2983
I don’t see temp but dividing your TAS by the mach number, your local speed of sound is maybe 20kts above standard(?).
You’re actually moving through the air at the 454kts, which in the thin air at FL390 the aircraft experiences as 237kts. You have a meaningful crosswind of 55kts pointed slightly aft enough causing you lose 5kts in GS from TAS.
It’s a good illustration of all speeds according to purpose. IAS as flying speed (dynamic pressure), TAS as progress through the air, GS how the wind affects TAS, Mach number keeping TAS within limits relative to speed of sound.
I mean, I assume no pilot has a need to do the above to pay any attention to the deviation in local speed of sound from standard. I included it because @AlexNine99 mentioned
And making the calculation illustrated the local speed of sound your aircraft is using is somewhat different from standard at that altitude.
Presumably temperature deviation is the culprit, as I assumed the altimeter setting difference from standard is not enough to explain the difference.
The main point is that, whatever the local speed of sound is, the mach number compares TAS to that somewhat dance-around “mystery” number.
edit: and the local speed of sound that is relevant for the mach number is itself a TAS (actual speed relative to the wind drifting airmass through which the aircraft flies. Example: a balloon carried along in a wind, even if blowing at the speed of sound, has a mach speed of 0).
