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max altitude and Mach 1 Now With Charts



 
 
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  #1  
Old May 14th 04, 11:13 PM
John R Weiss
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Posts: n/a
Default max altitude and Mach 1 Now With Charts

"Boomer" wrote...
the first chart is an F-16 (it SAYS F-15 but a look at the stats tells you
otherwise) Notice that it's Max altitude comes BEFORE Mach1.

the second chart is for an SU-30, it also reaches max alt BEFORE Mach1.

the third chart should be a F-4 vs MiG-21 notice these planes reach max

alt
well AFTER Mach 1


Curiosity killed the cat, and I'm gonna find out why!


From a non-aerodynamicist's point of view, there are several factors at
play. Any one of them may be limiting at a specific airspeed/altitude
combination.

The short answer is that the airplane is optimized for subsonic flight
(because it spends 99%+ of its life below Mach 1), so max altitude will be
attained at a subsonic speed.

Looking at the F-15 chart, because it is the "cleanest":

Below approx 38,000', max airspeed is placarded at 800 KCAS (for
discussion purposes, roughly equal to 800 KIAS). That is a structural
airframe limitation, and the engine might be able to push it faster until it
falls apart.

At the left side of the curve is Max Lift, or stall speed, and will
equate to a roughly constant Max Lift or "Stall" Angle of Attack. If you go
any slower, you start going down.

At approx 60,000' and Mach 0.95, you hit the peak of the envelope -- max
lift, max thrust, max drag. There is only one speed where the engine can
produce enough thrust to maintain altitude, and that is at Max Lift AoA.

When the airplane is transonic (here, above Mach 0.95), drag increases
significantly, before dropping off again at approx. Mach 1.05. The only way
to go faster if you start at 60K and .95 is to descend and accelerate. At
the same time, engine thrust is likely decreasing as the intake ramps and
exhaust nozzles are not controlling the airflow to and from the engines
perfectly. As the ramps and nozzles start re-configuring, thrust falls off
somewhat. By the time the thrust has recovered at Mach 1.05, drag is
starting to increase again, so the engine thrust limits performance up to
Mach 1.4. At that speed and approx 57,000', any further climb causes thrust
to decrease to the point where altitude and airspeed cannot be maintained.





  #2  
Old May 15th 04, 03:51 AM
Boomer
external usenet poster
 
Posts: n/a
Default

Were you able to see that charts I attached? Because my post with the charts
hasn't shown up on my system yet, I have NO idea why grrrr.

--



Curiosity killed the cat, and I'm gonna find out why!
"John R Weiss" wrote in message
news:3wbpc.50585$iF6.4560150@attbi_s02...
"Boomer" wrote...
the first chart is an F-16 (it SAYS F-15 but a look at the stats tells

you
otherwise) Notice that it's Max altitude comes BEFORE Mach1.

the second chart is for an SU-30, it also reaches max alt BEFORE Mach1.

the third chart should be a F-4 vs MiG-21 notice these planes reach max

alt
well AFTER Mach 1


Curiosity killed the cat, and I'm gonna find out why!


From a non-aerodynamicist's point of view, there are several factors at
play. Any one of them may be limiting at a specific airspeed/altitude
combination.

The short answer is that the airplane is optimized for subsonic flight
(because it spends 99%+ of its life below Mach 1), so max altitude will be
attained at a subsonic speed.

Looking at the F-15 chart, because it is the "cleanest":

Below approx 38,000', max airspeed is placarded at 800 KCAS (for
discussion purposes, roughly equal to 800 KIAS). That is a structural
airframe limitation, and the engine might be able to push it faster until

it
falls apart.

At the left side of the curve is Max Lift, or stall speed, and will
equate to a roughly constant Max Lift or "Stall" Angle of Attack. If you

go
any slower, you start going down.

At approx 60,000' and Mach 0.95, you hit the peak of the envelope --

max
lift, max thrust, max drag. There is only one speed where the engine can
produce enough thrust to maintain altitude, and that is at Max Lift AoA.

When the airplane is transonic (here, above Mach 0.95), drag increases
significantly, before dropping off again at approx. Mach 1.05. The only

way
to go faster if you start at 60K and .95 is to descend and accelerate. At
the same time, engine thrust is likely decreasing as the intake ramps and
exhaust nozzles are not controlling the airflow to and from the engines
perfectly. As the ramps and nozzles start re-configuring, thrust falls

off
somewhat. By the time the thrust has recovered at Mach 1.05, drag is
starting to increase again, so the engine thrust limits performance up to
Mach 1.4. At that speed and approx 57,000', any further climb causes

thrust
to decrease to the point where altitude and airspeed cannot be maintained.







  #3  
Old May 15th 04, 05:08 AM
John R Weiss
external usenet poster
 
Posts: n/a
Default

"Boomer" wrote...
Were you able to see that charts I attached?


Umm, yes... That's why I commented on them...



  #4  
Old May 15th 04, 05:57 AM
Boomer
external usenet poster
 
Posts: n/a
Default

thanks it still hasnt shown here.

--



Curiosity killed the cat, and I'm gonna find out why!
"John R Weiss" wrote in message
news:CIgpc.50861$536.8780260@attbi_s03...
"Boomer" wrote...
Were you able to see that charts I attached?


Umm, yes... That's why I commented on them...





  #5  
Old May 15th 04, 02:01 PM
Peter Stickney
external usenet poster
 
Posts: n/a
Default

In article ,
"Boomer" writes:
Were you able to see that charts I attached? Because my post with the charts
hasn't shown up on my system yet, I have NO idea why grrrr.


I wouldn't mind seeing them, but my news servers filter out binary
(image) posts sent to non-binary groups. If teh charts are on the
Web, may I ask that you post the URLs for them? If not, give a shout
& we'll arrange for you to E-Mail them.

--
Pete Stickney
A strong conviction that something must be done is the parent of many
bad measures. -- Daniel Webster
  #7  
Old May 15th 04, 05:49 PM
Boomer
external usenet poster
 
Posts: n/a
Default

btw, if anyone else wants to see them just send the same message.

--



Curiosity killed the cat, and I'm gonna find out why!
"Peter Stickney" wrote in message
...
In article ,
"Boomer" writes:
Were you able to see that charts I attached? Because my post with the

charts
hasn't shown up on my system yet, I have NO idea why grrrr.


I wouldn't mind seeing them, but my news servers filter out binary
(image) posts sent to non-binary groups. If teh charts are on the
Web, may I ask that you post the URLs for them? If not, give a shout
& we'll arrange for you to E-Mail them.

--
Pete Stickney
A strong conviction that something must be done is the parent of many
bad measures. -- Daniel Webster



 




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