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Swiss A340 Cruising At Mach ONE?  
User currently offlineWardialer From United States of America, joined Sep 2001, 1183 posts, RR: 0
Posted (5 years 1 week 1 day 20 hours ago) and read 6800 times:

Check this out from Flightaware....And scroll down until you see that the speed hits MACH 1.04...Just scroll down until you see Gander Center...And you will see it...

Is this true or what???

http://flightaware.com/live/flight/S.../20091016/0234Z/KLAX/LSZH/tracklog

28 replies: All unread, showing first 25:
 
User currently onlineLemmy From United States of America, joined Dec 2004, 260 posts, RR: 0
Reply 1, posted (5 years 1 week 1 day 20 hours ago) and read 6796 times:

That's probably the equivalent speed in still air. They must have had a nice tailwind, which would mean that their indicated speed was much lower.


I am a patient boy ...
User currently offlineWardialer From United States of America, joined Sep 2001, 1183 posts, RR: 0
Reply 2, posted (5 years 1 week 1 day 20 hours ago) and read 6789 times:

Yes, I had flown Swiss many time from KLAX to Zurich, and the Eastbound flights do have a nice tailwind always in that area...

So, would this be the True Mach speed, or please explain.....

I though aircrafts over land cannot do Mach 1 at all because it may cause a SONIC BOOM...
So please explain why this log indicates Mach 1.

Also, this is interesting....How can I find an online calculator that will convert the Alt, Ground Speed, IAS, to the Mach number like that log??? So I need to find out how the log calculated a speed of Mach 1 at FL350 that would be equivalent to still air.....

Because flying at actual MACH 1 speed would of had caused a Sonic Boom.....


How can this be done using a calculator or something....????

[Edited 2009-10-16 13:34:41 by wardialer]

[Edited 2009-10-16 13:36:19 by wardialer]

User currently offlineFLY2HMO From , joined Dec 1969, posts, RR:
Reply 3, posted (5 years 1 week 1 day 20 hours ago) and read 6762 times:

Quoting Lemmy (Reply 1):
That's probably the equivalent speed in still air.

Groundspeed is the correct term.

Quoting Wardialer (Reply 2):
So, would this be the True Mach speed, or please explain.....

Mach speed is Mach speed, there are no other variations of it.

Quoting Wardialer (Reply 2):
So please explain why this log indicates Mach 1.

It is not doing mach 1 per se. And there is no sonic boom. Mach speed is in relation to the air, altitude, pressure and temperature. This high groundspeed is a product of a strong tailwind. Online tracking services can only show groundspeed as it is radar based information.

[Edited 2009-10-16 13:38:20]

User currently offlineWardialer From United States of America, joined Sep 2001, 1183 posts, RR: 0
Reply 4, posted (5 years 1 week 1 day 20 hours ago) and read 6770 times:

Ok, i understand....But not quite.

All I wish to have or do, is calculate this the same way as in the log above.

So for example, how did they get Mach 1.04 at a Ground Speed of 690 knots at FL350?
Now, of course, we cannot tell at which IAS Airspeed or even the temp. at that altitude from this tracking service....But lets all assume that it was like something at a temp -48 C and an IAS of 280 knots...

I just need to know how they came up with the Mach 1 number relative to that Ground Speed at FL350???


User currently offlineFLY2HMO From , joined Dec 1969, posts, RR:
Reply 5, posted (5 years 1 week 1 day 20 hours ago) and read 6765 times:



Quoting Wardialer (Reply 4):
I just need to know how they came up with the Mach 1 number relative to that Ground Speed at FL350???

They are probably interpolating standard temps for the given altitudes and doing a conversion like you would from say, kmh to mph


User currently offline71Zulu From United States of America, joined Aug 2006, 3086 posts, RR: 0
Reply 6, posted (5 years 1 week 1 day 19 hours ago) and read 6758 times:

Yep, Flightaware only tracks groundspeed. The mach figures are the equivalent ground speed in knots taking the tailwind into consideration.

Check some speed records here,

http://www.groundspeedrecords.com/database%20commercial.htm

Current record of those submitted for the A343 is 721 knots.



The good old days: Delta L-1011s at MSY
User currently offlineA342 From Germany, joined Jul 2005, 4689 posts, RR: 3
Reply 7, posted (5 years 1 week 1 day 19 hours ago) and read 6741 times:



Quoting Wardialer (Reply 4):
So for example, how did they get Mach 1.04 at a Ground Speed of 690 knots at FL350?

For example if the aircraft flies at an airspeed of M0.82 (normal A340 cruise speed) and the tailwind adds the equivalent of M0.22.

A342



Exceptions confirm the rule.
User currently offlineRwessel From United States of America, joined Jan 2007, 2368 posts, RR: 2
Reply 8, posted (5 years 1 week 1 day 19 hours ago) and read 6728 times:
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Quoting Wardialer (Reply 2):
Also, this is interesting....How can I find an online calculator that will convert the Alt, Ground Speed, IAS, to the Mach number like that log??? So I need to find out how the log calculated a speed of Mach 1 at FL350 that would be equivalent to still air.....

This one is my favorite:

http://www.aerospaceweb.org/design/scripts/atmosphere/


User currently offlineTdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 9, posted (5 years 1 week 1 day 18 hours ago) and read 6683 times:



Quoting Wardialer (Reply 2):
Because flying at actual MACH 1 speed would of had caused a Sonic Boom.....

Not necessarily...Mach 1 groundspeed may not be Mach 1 at the aircraft...you need to be supersonic at the aircraft to generate a shock wave.

In addition, speed of sound drops with altitude (at commercial jet heights), so even if the aircraft is generating a shock wave it may not propagate to the ground. Some of the supersonic BBJ concepts use this effect to go supersonic without causing an audible boom on the ground.

Tom.


User currently offlineSoon7x7 From , joined Dec 1969, posts, RR:
Reply 10, posted (5 years 1 week 1 day 16 hours ago) and read 6634 times:

Last April we had a "Noreaster in New York"...dumped 10" of snow...("Noreasters are famous for intense winds, both surface and aloft")...the next day I departed JFK to Geneva...wheels up to wheels down=6 hours....we caught the lower side of the low off on St. Johns Bay and it sling shot us eastward. At 35K the outside temp was-86F...we had to descend to 27,000ft. Had just enough time for two meals and to listen to five cd's!...j

User currently offlineWardialer From United States of America, joined Sep 2001, 1183 posts, RR: 0
Reply 11, posted (5 years 1 week 1 day 10 hours ago) and read 6511 times:

Ok, thanks for the great links.
So, just to conclude this....The Mach 1 speed thats in that track log is NOT the same as going actually at Mach 1 (the speed of sound)???

So in that log, the Mach 1 speed is actually the MACH Ground Speed and not the same as the Mach number which indicated on the Airspeed dials???

I did not know that there are two versions of Mach numbers...

So theres Mach ground speed and the Mach speed that is on the IAS Airspeed dials??


User currently offlineRwessel From United States of America, joined Jan 2007, 2368 posts, RR: 2
Reply 12, posted (5 years 1 week 1 day 9 hours ago) and read 6493 times:
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Quoting Wardialer (Reply 11):
So, just to conclude this....The Mach 1 speed thats in that track log is NOT the same as going actually at Mach 1 (the speed of sound)???

Correct.

Quoting Wardialer (Reply 11):
So in that log, the Mach 1 speed is actually the MACH Ground Speed and not the same as the Mach number which indicated on the Airspeed dials???

I did not know that there are two versions of Mach numbers...

So theres Mach ground speed and the Mach speed that is on the IAS Airspeed dials??

There isn't really. "Mach ground speed" is basically a useless bit of information. FlightAware presumably only knows the actual speed of the aircraft relative to earth (IOW, the groundspeed). They're presumably computing the other numbers from that, *without* knowing the exact conditions aloft (specifically wind speed, temperature and pressure), and just assuming that standard conditions apply.


User currently offlineTripleDelta From Croatia, joined Jul 2004, 1123 posts, RR: 7
Reply 13, posted (5 years 1 week 1 day 6 hours ago) and read 6419 times:
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Quoting Wardialer (Reply 11):
So, just to conclude this....The Mach 1 speed thats in that track log is NOT the same as going actually at Mach 1 (the speed of sound)???

One could also use the old "walking in a train" concept to explain why the ground speed is in the supersonic range and the aircraft's speed is still subsonic.

Imagine that you have a train doing 100 mph. And you have a person in the train walking/running at say 5 mph in the direction in which the train is traveling. His speed in relation to the ground would be 100+5 mph, because the train is moving relative to the ground and the person is moving relative to the train. If the person would be walking in the opposite direction, his "groundspeed" would be 100-5 mph and so on...

In flight, the aircraft is the passenger and the moving airmass - or wind - is the train. The indicated airspeed you read of the ASI and the Mach number are measured relative to the air mass, not the ground. So if an aircraft has a cruise speed of M0.8, that means that it's flying at that Mach relative to the air. And if the air itself is moving in the same direction at say M0.3, the speed of the aircraft relative to the ground is M0.8 + M0.3 -> M1.1 - that is, it's groundspeed is such as if the aircraft were doing M1.1 in still air.

EDIT: for clarification  

[Edited 2009-10-17 03:45:06]

[Edited 2009-10-17 03:50:00]


No plane, no gain.
User currently offlineCosmicCruiser From United States of America, joined Feb 2005, 2255 posts, RR: 15
Reply 14, posted (5 years 1 week 1 day 2 hours ago) and read 6324 times:



Quoting FLY2HMO (Reply 3):
Groundspeed is the correct term.

Right on. The confusion here is the fact that this flight tracker or whatever gave the GS in Mach. That's a little bit of a stretch and I've never thought of GS in Mach. He was probably doing .82 and had 175 kts + on the tail, not uncommon in the winter.


User currently offlineFLY2HMO From , joined Dec 1969, posts, RR:
Reply 15, posted (5 years 1 week 22 hours ago) and read 6249 times:



Quoting Wardialer (Reply 11):
I did not know that there are two versions of Mach numbers...

There aren't two. Like I said in my first post, there's only one type of Mach speed. It's impossible for flightaware to know the plane's actual Mach speed short of them having the pilots radio them the information. Flightaware is just guesstimating it using the ground speed in knots as a reference.

Quoting TripleDelta (Reply 13):

In flight, the aircraft is the passenger and the moving airmass - or wind - is the train. The indicated airspeed you read of the ASI and the Mach number are measured relative to the air mass, not the ground. So if an aircraft has a cruise speed of M0.8, that means that it's flying at that Mach relative to the air. And if the air itself is moving in the same direction at say M0.3, the speed of the aircraft relative to the ground is M0.8 + M0.3 -> M1.1 - that is, it's groundspeed is such as if the aircraft were doing M1.1 in still air.

Excellent explanation.  yes 

Quoting CosmicCruiser (Reply 14):
He was probably doing .82

Sounds about right.


User currently offlineDocLightning From United States of America, joined Nov 2005, 19953 posts, RR: 59
Reply 16, posted (5 years 1 week 17 hours ago) and read 6164 times:



Quoting FLY2HMO (Reply 3):

Groundspeed is the correct term.

On a trip in early February from EWR to LHR on a BA 777, our groundspeed was, at points, in excess of 770 MPH. We made the trip in under 5 hours. That's not a heck of a lot worse than Concorde.

The trip back was almost 8 hours.  crowded 


User currently offlineLIFFY1A From Ireland, joined Jan 2008, 120 posts, RR: 0
Reply 17, posted (5 years 1 week 17 hours ago) and read 6157 times:



Quoting FLY2HMO (Reply 3):
Mach speed is in relation to the air, altitude, pressure and temperature.

Correct me if I'm wrong, but is the mach no. not affected by the temperature of the air and that only.


User currently offlineTdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 18, posted (5 years 1 week 17 hours ago) and read 6147 times:



Quoting LIFFY1A (Reply 17):
Correct me if I'm wrong, but is the mach no. not affected by the temperature of the air and that only.

Speed of sound in most gases is a function of the temperature (and the gas) only. Assuming we're talking standard air at normal pressures all the time, then it's just a function of temperature.

Mach number is a function of airspeed and local speed of sound or, equivalently, airspeed and local temperature.

Tom.


User currently offlineLIFFY1A From Ireland, joined Jan 2008, 120 posts, RR: 0
Reply 19, posted (5 years 1 week 17 hours ago) and read 6129 times:



Quoting Tdscanuck (Reply 18):
Mach number is a function of airspeed and local speed of sound or, equivalently, airspeed and local temperature.

Would I be correct in saying, for example, if you have a TAS of 400kts, and a Mach No. of .82, then if the TAS remains constant and the temperature changes, then the Mach No. will change regardless of changes in pressure?


User currently offlineWardialer From United States of America, joined Sep 2001, 1183 posts, RR: 0
Reply 20, posted (5 years 1 week 12 hours ago) and read 6043 times:

I actually needed a calculator that would allow me to convert TAS, Ground Speed, and the equivelant Mach number relative to "still air"

So for example....

If I was flying at a TAS of 480 kts with a tailwind of 100 kts that would of course be a GS of 580 kts. What I want to know from this point, is the Mach number that would be equivelant to still air, like in that flight tracking log.....

The online calculator below will not give me the Ground Speed Mach number, it only gives or converts it to the aircraft's Mach number relative to the air mass, and not relative to the ground.

In other words, by using the online calculator below, is there any way of knowing the "ground-relative" Mach Number (also refered to as Ground Speed Mach) rather than the Mach measured relative to the air mass?

I understand the difference between TAS and Ground Speed, but I want to convert the Mach number used in Airspeed Indicators to the Mach number relative to the groundspeed just the way that flight log does.

http://www.aerospaceweb.org/design/scripts/atmosphere/


User currently offlineFLY2HMO From , joined Dec 1969, posts, RR:
Reply 21, posted (5 years 1 week 12 hours ago) and read 6039 times:



Quoting Wardialer (Reply 20):
I actually needed a calculator

Google to the rescue...

http://www.globalaircraft.org/converter.htm


User currently offlineTdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 22, posted (5 years 1 week ago) and read 5840 times:



Quoting LIFFY1A (Reply 19):

Would I be correct in saying, for example, if you have a TAS of 400kts, and a Mach No. of .82, then if the TAS remains constant and the temperature changes, then the Mach No. will change regardless of changes in pressure?

Yes. It will change proportional to the square root of the temperature.

Tom.


User currently offlineHaveBlue From United States of America, joined Jan 2004, 2116 posts, RR: 1
Reply 23, posted (5 years 6 days 23 hours ago) and read 5827 times:

Mach is the speed an aircraft is traveling.... in relation to the air around it. Another words at sea level on a standard day the aircraft would have to be going 760 mph faster than the air it is in. So if its doing 700mph, and a tail wind is pushing it 60 mph faster, the aircraft is still subsonic. It is doing 700 mph on its airspeed indicator in the cockpit, it is going 700 mph faster than the air it is traveling in, but its groundspeed is 760mph which is equivalent to Mach 1.

The sonic boom comes from the overpressure of air not being able to get out of the way of the aircraft as it goes supersonic. This happens (for our example) when the plane is going 760 mph faster than the air it is traveling thru. So it is irrelevant if the plane is going 740mph indicated and has a 200 mph tailwind, it is still subsonic... though it would have a hell of a groundspeed of 940mph. Groundspeed simply being the amount of ground that is covered in a given timeframe and is completely irrelevant to the aircraft itself.

Think of it this way. Your in a boat this only capable of doing 10mph, period. Well if you have the throttle wide open but the river your running in is doing 5mph the same direction, then your boat will be covering ground at 15mph. Consequently if that same boat is going against that same tide it would be only covering ground at 5mph. The boat is still doing 10mph thru the water either way, but its progress overall will be dependent how fast the stream its moving in is going.

You see the wing on the airplane doesn't care about groundspeed. It will go supersonic or stall depending on the aircrafts speed thru the air its moving in. Regardless of how fast that air is moving. This is how we hovered Cessna's in flight school. The Cessna 152 stalls at 40 knots without the flaps down. So put your nose into a 40 knot headwind and you are hovering over the same spot on the ground. Now we know the Cessna cannot hover, it is moving thru the air at 40 knots but the air is moving it backwards at 40 knots, which means we aren't progressing over the ground. Now turn the plane around at that same 40 knots and now we're covering ground at 80 knots groundspeed without changing anything but direction.

Hope that helps. The groundspeeds you see on flightaware and in the plane on the map track having nothing at all to do with supersonic or shockwaves. Supersonic is how fast YOU are traveling THRU the air, regardless of how fast the air may be moving you along.

[Edited 2009-10-18 10:07:29]


Here Here for Severe Clear!
User currently offlineFLY2HMO From , joined Dec 1969, posts, RR:
Reply 24, posted (5 years 6 days 22 hours ago) and read 5783 times:

So what happens if you grab a runway and make it into a giant conveyor belt?  duck   duck   duck 

25 HaveBlue : Then you've just flogged a very dead horse to death again. lol.
26 DocLightning : We take you out back and beat the crap out of you?
27 Post contains links FlybaurLAX : Mach is just a unitless number that is a ratio of relative speed to the speed of sound (at that altitude). As stated before, it's a function of tempe
28 113312 : Flightaware is not doing anyone a service by displaying incorrect and erroneous data. Mach number is the aircraft's true airspeed relative to the spee
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