Let's talk "overspeed"

[Jake Bourdon]

I'm sure many of you Flight Simulator X and FS9 players are aware that commercial airliners easily cruise at speeds around 450-480 knots. Well, unfortunately FSX doesn't let you reach that cruise speed without saying overspeed and all the systems beeping and what not. Is there any way to fix this so that the overspeed alarms and everything are up at around 500 knots or so?

-Jake

[Strategic Retreat]

What is overspeed in a plane?

Spoken about in a brief, concise, and down to earth way is the maximum speed the cell of the plane can travel in the air before said cells begins disintegrating for effects of localized supersonic shockwaves (I'm not going to cover dirtied configuration overspeed here, thing that happen with flaps and/or gear down but cruise overspeed, seen that FS warns only about this kind of excessive speed) and its Kias changes with local barometric pressure, flight level and temperature. This is why it is usually expressed in the more constant Mach number.

Example, the maximum speed of the B747 is about Mach .94, if I remember correctly, but usually the overspeed horn begins blaring at a much lower speed, seen that reaching the borderline speeds is dangerous for the safety of the plane. Maximum cruise speed for a 747 is Mach .855 (nowadays rarely reached because of economic reasoning, seen that keeping lower cruise speeds makes for much lower fuel consumption and not much slower cruise speeds) as stated by Boeing, and if you try and go over it... Overspeed Horn!

Now, I don't want to either paint myself as a know-it-all nor to downplay your flying ability, but exactly at what Mach speed are you trying to travel that you have this problem with overspeed? :-?

[Brett_Henderson]

The overspeed alarm is tied to INDICATED airspeed..

The 400-500 knot cruise speed, at high altitudes, is a much lower indicated airspeed.

A rough calculation can be 2% per 1000msl..

250kias at 40,000msl..

[Brett_Henderson]

And yes.. as Strategic Retreat points out..

[Strategic Retreat]

The overspeed alarm is tied to INDICATED airspeed.

On what planes exactly? :-?

If we're speaking about cell max overspeed... it just CAN'T be tied to indicated airspeed, unless on smaller, much smaller planes than a liner.

[Brett_Henderson]

The overspeed alarm is tied to INDICATED airspeed.

On what planes exactly? :-?

If we're speaking about cell max overspeed... it just CAN'T be tied to indicated airspeed, unless on smaller, much smaller planes than a liner.

I'm talking about the MSFS overspeed; not real airliners.. it's trigger is the indicated airspeed

[Capt.Propwash]

look in the aircraft.cfg file, near the bottom

[Reference Speeds]
flaps_up_stall_speed    = 142.0                 //Knots True (KTAS)
full_flaps_stall_speed  = 113.0                 //Knots True (KTAS)
cruise_speed            = 477.0                 //Knots True (KTAS)
max_mach                = 0.82
max_indicated_speed     = 340                   //Red line (KIAS)


make these numbers higher


This came from the default B737-800 FSX

[Strategic Retreat]

I'm talking about the MSFS overspeed; not real airliners.. it's trigger is the indicated airspeed

Ah. Fundamentally true. Even though there are some add-on, even freeware ones like the Project Mach 2 Concorde (not available anymore on the net since the PM2 site fell and their inexplicable refusal to release the package elsewhere), that do an admirable job trying to work around this fact... FS is not X-plane.

[Brett_Henderson]

I'm talking about the MSFS overspeed; not real airliners.. it's trigger is the indicated airspeed

Ah. Fundamentally true. Even though there are some add-on, even freeware ones like the Project Mach 2 Concorde (not available anymore on the net since the PM2 site fell and their inexplicable refusal to release the package elsewhere), that do an admirable job trying to work around this fact... FS is not X-plane.

MSFS works around it too.. however, not until above 20,000msl.

If you want to understand it a bit better.. the defaul KingAir is equipped with a "barber-pole" on the ASI. You can fiddle with the max_indicated_speed number in the cfg file, and then load the KingAir to see the overspeed needle move in realtionship.

Now.. as you climb, the needle doesn't move, UNTIL you pass 20,000msl.. then it starts moving down. That's MSFS' way of transitioning to mach-numbers, but in reality it's just an attenuation of the airspeed set in the cfg file. The overspeed alarm is still looking for an indicated airspeed.

In the real world that attenuation should happen during any increase in altitude. It's certainly not an exact interpretation of how airspeed and mach relate, but it's more than adequate for a desktop simulator, and a virtual pilot trying to accurately manage his speeds.

I'm not familiar with how Xplanes deals with it, but I'd bet it's no more sophisticated. As for payware, or 3rd party stuff.. the sky is literally the limit..

[Jake Bourdon]

Thank you all so much for your mind-blowing comments! I especially thank Strategic Retreat and Brett Henderson. You guys taught me something that I completely forgot about. I'm a new fsx commercial pilot and am hoping to learn as much as I can about commercial and executive jets, so I can have my dream career, having an ATP and flying "the jumbo's" once I get out of college(I'm currently 15 and won't be starting college until I get out of high-school). Thank you all so much, I'm astonished with the responses. I hope you all have a great weekend