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Colt160
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Can Boeing 777-300ER go faster than speed of sound?

Wed Jun 15, 2016 2:02 pm

My wife recently flied on CX840 from Hong Kong To JFK. I checked her flight out on flightware.com and found something interesting. The flight recorded 829 KTS (I assume it is Knot ground speed). The speed of sound in Knots is 666. So she was flying 150 knots faster than speed of sound? Wondering if the plane can hold in one piece.... Have trouble to link the picture. Hope you can check out the handphone screen capture for reference.




https://photos.google.com/share/AF1QipP ... plc2hidmdn

https://photos.google.com/share/AF1QipP ... plc2hidmdn
 
caverunner17
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Re: Can Boeing 777-300ER go faster than speed of sound?

Wed Jun 15, 2016 2:15 pm

The speed you saw is ground speed. Ground speed is speed of the plane + or - wind speed. What this means is that there was a tailwind. The plane itself was probably going 500-550mph, relative to the wind-speed
 
LSZH34
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Re: Can Boeing 777-300ER go faster than speed of sound?

Wed Jun 15, 2016 2:17 pm

That was the ground speed. The speed relative to the air is still sub-sonic. Civil airliners are not designed to fly super-sonic. Mmo for the B777 is M.89 and they won't exceed that limit.
 
coolian2
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Re: Can Boeing 777-300ER go faster than speed of sound?

Wed Jun 15, 2016 2:19 pm

It could do the speed of sound but probably not in one piece.
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Colt160
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Re: Can Boeing 777-300ER go faster than speed of sound?

Wed Jun 15, 2016 2:24 pm

That is still rather "spectacular". If the plane has a speed of 555 knots. The tail wind speed is 274 knots. Hurricane Katrina highest wind speed is only 150 knots. It is almost twice the Katrina..... A plane inside Double Katrina still can fly?
 
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tjwgrr
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Re: Can Boeing 777-300ER go faster than speed of sound?

Wed Jun 15, 2016 2:44 pm

How about warp factor 3? Can a 777-300ER handle that?
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trnswrld
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Re: Can Boeing 777-300ER go faster than speed of sound?

Wed Jun 15, 2016 2:47 pm

Colt160 wrote:
That is still rather "spectacular". If the plane has a speed of 555 knots. The tail wind speed is 274 knots. Hurricane Katrina highest wind speed is only 150 knots. It is almost twice the Katrina..... A plane inside Double Katrina still can fly?

Think of it like this, the plane is just cruising along in a air mass at normal speeds it was designed to fly at, it just happens to be in an air mass moving at a high speed in the same direction. Imagine you are walking through an airport terminal on the ground at a constant speed of 2mph, then you walk right onto one of those moving conveyor platforms (escalator looking things). Now all of a sudden you picked up a another 2 mph (essentially doubling your speed), but you're not actually walking any faster. Does that kind of make sense?
 
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Colt160
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Re: Can Boeing 777-300ER go faster than speed of sound?

Wed Jun 15, 2016 2:57 pm

trnswrld wrote:
Colt160 wrote:
That is still rather "spectacular". If the plane has a speed of 555 knots. The tail wind speed is 274 knots. Hurricane Katrina highest wind speed is only 150 knots. It is almost twice the Katrina..... A plane inside Double Katrina still can fly?

Think of it like this, the plane is just cruising along in a air mass at normal speeds it was designed to fly at, it just happens to be in an air mass moving at a high speed in the same direction. Imagine you are walking through an airport terminal on the ground at a constant speed of 2mph, then you walk right onto one of those moving conveyor platforms (escalator looking things). Now all of a sudden you picked up a another 2 mph (essentially doubling your speed), but you're not actually walking any faster. Does that kind of make sense?



Yes I can understand the physical but up in the Bering Sea with the jetstream twice as fast as Katrina, I think it is more than a joy ride on a smooth flying carpet. I am no pilot so I do not know. Just see this data kind of amazing
 
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Re: Can Boeing 777-300ER go faster than speed of sound?

Wed Jun 15, 2016 3:09 pm

coolian2 wrote:
It could do the speed of sound but probably not in one piece.


I'm sure it could. A DC-8 exceeded the speed of sound during flight test. Any other model probably could do it.
 
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Re: Can Boeing 777-300ER go faster than speed of sound?

Wed Jun 15, 2016 3:30 pm

Didn't a TWA 727 exceed the sound barrier once in a descent after some sort of issue that may have been pilot induced? Messing with flap settings to get a slightly higher cruise speed (or something I cant remember), then something went wrong and they got into a uncontrollable decent? They ended up pulling out of it, but parts of the aircraft were damaged in the process of trying to slow down and recover.
 
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Re: Can Boeing 777-300ER go faster than speed of sound?

Wed Jun 15, 2016 4:03 pm

Colt160 wrote:
The speed of sound in Knots is 666.


At the flight level the airplane would have been at, Mach 1 would have been way lower than this.


https://photos.google.com/share/AF1QipP ... plc2hidmdn

https://photos.google.com/share/AF1QipP ... plc2hidmdn
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Re: Can Boeing 777-300ER go faster than speed of sound?

Wed Jun 15, 2016 4:06 pm

trnswrld wrote:
Didn't a TWA 727 exceed the sound barrier once in a descent after some sort of issue that may have been pilot induced? Messing with flap settings to get a slightly higher cruise speed (or something I cant remember), then something went wrong and they got into a uncontrollable decent? They ended up pulling out of it, but parts of the aircraft were damaged in the process of trying to slow down and recover.


I think that's right. Unfortunately, PSA 1771 exceeded the speed of sound too.

As mentioned, all civil airplanes could probably exceed the speed of sound just like the test DC-8 did. However, I suspect it's now prohibited, just like barrel rolling is, even though that can be done completely safely if done correctly.
 
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Re: Can Boeing 777-300ER go faster than speed of sound?

Wed Jun 15, 2016 5:30 pm

Colt160 wrote:
The speed of sound in Knots is 666.


That was your mistake.
 
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Re: Can Boeing 777-300ER go faster than speed of sound?

Wed Jun 15, 2016 5:55 pm

BoeingGuy wrote:
I think that's right. Unfortunately, PSA 1771 exceeded the speed of sound too.

As did MS990 and NG004... both of which began to break up as a result. :(
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Utah744
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Re: Can Boeing 777-300ER go faster than speed of sound?

Wed Jun 15, 2016 6:28 pm

Just once. :lol:
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Re: Can Boeing 777-300ER go faster than speed of sound?

Wed Jun 15, 2016 6:44 pm

Utah744 wrote:
Just once. :lol:


I'd beg to differ. The DC-8 exceeded the speed of sound and was in service for another 20 years. With the exception of the TWA 727, the other airplanes mentioned were not in controlled flight.

It's a bit academic because it will likely not be tested, but if you put a 777-300ER in a controlled environment and exceeded Mach 1, just like was done with that DC-8, I'm willing to bet the airplane would do just fine.
 
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Re: Can Boeing 777-300ER go faster than speed of sound?

Wed Jun 15, 2016 7:12 pm

No it wont be fine. Max Operating Speed is .89 Mach for 7773ER. They certainly don't test it to Mach 1. The Never Exceed Speed (Vne) and Max Dive speeds are based on flutter testing and not some goal to hit mach 1.

Can the airplane survive Mach 1... not for very long and you would need to do a massive inspection afterwards since you probably damaged something as you are well into the flutter ranges. Anything .90 mach and over would require significant airframe inspections. MMO for a 772 is .87 so its even less.

And please dont bring up super critical airfoils and local mach number at some location on the wing... that is not what this is about.
 
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Re: Can Boeing 777-300ER go faster than speed of sound?

Wed Jun 15, 2016 7:54 pm

pygmalion wrote:
No it wont be fine. Max Operating Speed is .89 Mach for 7773ER. They certainly don't test it to Mach 1. The Never Exceed Speed (Vne) and Max Dive speeds are based on flutter testing and not some goal to hit mach 1.

Can the airplane survive Mach 1... not for very long and you would need to do a massive inspection afterwards since you probably damaged something as you are well into the flutter ranges. Anything .90 mach and over would require significant airframe inspections. MMO for a 772 is .87 so its even less.

And please dont bring up super critical airfoils and local mach number at some location on the wing... that is not what this is about.


I'm aware of the exact Mmo/Vmo thresholds for most Boeing models. A different way to ask this question is why did the flight test DC-8 easily survive exceeding Mach 1, yet the 777-300ER cannot?
 
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Re: Can Boeing 777-300ER go faster than speed of sound?

Wed Jun 15, 2016 8:44 pm

I once flew on a UA 747 routing LAS-ORD back in 1982 or thereabouts that caught a great tailwind. The pilot said it added 150 knots to our speed and we were cruising at about 650kts. I think he was likely referring to the ground speed we picked up. As a result, we were 35 minutes early into ORD. :lol:
 
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Re: Can Boeing 777-300ER go faster than speed of sound?

Wed Jun 15, 2016 8:57 pm

BoeingGuy wrote:
Utah744 wrote:
Just once. :lol:


the other airplanes mentioned were not in controlled flight


I recall reading somewhere that that FX DC-10 that had the FE go nuts and try to kill the pilots, went above the speed of sound. Of course that thing was out of control for a short bit, but was recovered and made a safe landing. What ever happened to that plane?
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airboeingbus
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Re: Can Boeing 777-300ER go faster than speed of sound?

Wed Jun 15, 2016 9:24 pm

Don't specifically know about the 777, but i remember when watching the A380 production documentary, during the flutter test they pushed the frame to over Mach 1.
 
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Re: Can Boeing 777-300ER go faster than speed of sound?

Wed Jun 15, 2016 9:46 pm

airboeingbus wrote:
Don't specifically know about the 777, but i remember when watching the A380 production documentary, during the flutter test they pushed the frame to over Mach 1.

Unless it was different from the one I watched, they only hit 0.96 Mach.
https://www.youtube.com/watch?v=ImSuZjvkATw
 
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Re: Can Boeing 777-300ER go faster than speed of sound?

Wed Jun 15, 2016 11:59 pm

LSZH34 wrote:
The speed relative to the air is still sub-sonic.

Actually more than likely transonic.
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Re: Can Boeing 777-300ER go faster than speed of sound?

Thu Jun 16, 2016 12:28 am

trnswrld wrote:
Didn't a TWA 727 exceed the sound barrier once in a descent after some sort of issue that may have been pilot induced? Messing with flap settings to get a slightly higher cruise speed (or something I cant remember), then something went wrong and they got into a uncontrollable decent? They ended up pulling out of it, but parts of the aircraft were damaged in the process of trying to slow down and recover.


There was no evidence to confirm the actual speed in the accident report so it's just speculation that it exceeded Mach 1.
 
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Re: Can Boeing 777-300ER go faster than speed of sound?

Thu Jun 16, 2016 1:33 am

b747400erf wrote:
Colt160 wrote:
The speed of sound in Knots is 666.


That was your mistake.



I am not sure what you mean. But I did google it and there is no mistake.
A plane flying Mach 1.0 at sea level is flying about 1225 km/h (661 Knots, 761 mph), a plane flying Mach 1.0 at 30000 ft is flying 1091 km/h (589 knots, 678 mph) etc.
 
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Colt160
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Re: Can Boeing 777-300ER go faster than speed of sound?

Thu Jun 16, 2016 1:36 am

ILNFlyer wrote:
I once flew on a UA 747 routing LAS-ORD back in 1982 or thereabouts that caught a great tailwind. The pilot said it added 150 knots to our speed and we were cruising at about 650kts. I think he was likely referring to the ground speed we picked up. As a result, we were 35 minutes early into ORD. :lol:


Noted about the 150 kts tail wind, it is Katrina grade. But the 777 did 829 kts. The tail wind is twice the Katrina.......
 
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Re: Can Boeing 777-300ER go faster than speed of sound?

Thu Jun 16, 2016 1:43 am

Colt160 wrote:
Noted about the 150 kts tail wind, it is Katrina grade. But the 777 did 829 kts. The tail wind is twice the Katrina.......


The winds at cruising altitudes can be quite magnificent. I have frequently flown at (ground) speeds in excess of 650 mph in aircraft like the 77W and the 763. In many cases, the flights have been smooth as anything. You only really feel turbulence when you're moving between different wind streams.

The thing with typhoons and hurricanes isn't so much the wind speed as the changes in wind speed/direction caused by things that get in the way -- whether those things are manmade (buildings, bridges, ships etc.) or natural (mountains, trees, waves, etc.). Up at 35,000 feet, there are not many things to get in the way of the wind and thus cause turbulence and/or damage.
 
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Re: Can Boeing 777-300ER go faster than speed of sound?

Thu Jun 16, 2016 1:49 am

So you mean the 829 KTS on a 777 is doable and normal in that case? I am just a passenger in a metal tube. Just find this is rather interesting.
 
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Re: Can Boeing 777-300ER go faster than speed of sound?

Thu Jun 16, 2016 2:03 am

Colt160 wrote:
So you mean the 829 KTS on a 777 is doable and normal in that case? I am just a passenger in a metal tube. Just find this is rather interesting.


I'm just a passenger too ... but I hope I have learned a few things from the experts I've encountered.

I'm not sure 829 KTS would be considered "normal" -- it sounds pretty exceptional to me. However, there are a couple of things that perhaps need explaining.

Tracking sites such as FlightAware, etc., use ground speeds: That is the speed the aircraft is moving across the ground.

Aircraft speed (and thus Mach numbers) work in relative terms: That is they are measured relative to the air around the aircraft, and it is delivered to the pilot as an indicated speed. If there is zero wind, then the indicated airspeed will be the same as the ground speed.

For example, if the aircraft is doing a constant INDICATED 200 KTi (the "i" means indicated here):
Zero wind: The ground speed is 200 KT.
100 KT headwind: Ground speed is 100 KT (200 KTi - 100 KT headwind)
100 KT tailwind: Ground speed is 300 KT (200 KTi + 100 KT tailwind)

In all three cases, the aircraft is still travelling at 200 KT relative to the air around it. This is the important thing to remember ... everything is relative to the air around the aircraft. So, the aircraft thinks it is travelling at 200 KT all the time, while FlightAware has it travelling at all sorts of different numbers.

If the airflow is perfectly linear, then a passenger will have no idea of how fast they are moving and won't experience any turbulence. It's only once the airflow ceases to be linear that the turbulence will be experienced.

This is a highly simplified explanation, but it's pretty much how I understand the mechanics of flight speed.
 
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Re: Can Boeing 777-300ER go faster than speed of sound?

Thu Jun 16, 2016 2:18 am

BreninTW wrote:
Colt160 wrote:
So you mean the 829 KTS on a 777 is doable and normal in that case? I am just a passenger in a metal tube. Just find this is rather interesting.


I'm just a passenger too ... but I hope I have learned a few things from the experts I've encountered.

I'm not sure 829 KTS would be considered "normal" -- it sounds pretty exceptional to me. However, there are a couple of things that perhaps need explaining.

Tracking sites such as FlightAware, etc., use ground speeds: That is the speed the aircraft is moving across the ground.

Aircraft speed (and thus Mach numbers) work in relative terms: That is they are measured relative to the air around the aircraft, and it is delivered to the pilot as an indicated speed. If there is zero wind, then the indicated airspeed will be the same as the ground speed.

For example, if the aircraft is doing a constant INDICATED 200 KTi (the "i" means indicated here):
Zero wind: The ground speed is 200 KT.
100 KT headwind: Ground speed is 100 KT (200 KTi - 100 KT headwind)
100 KT tailwind: Ground speed is 300 KT (200 KTi + 100 KT tailwind)

In all three cases, the aircraft is still travelling at 200 KT relative to the air around it. This is the important thing to remember ... everything is relative to the air around the aircraft. So, the aircraft thinks it is travelling at 200 KT all the time, while FlightAware has it travelling at all sorts of different numbers.

If the airflow is perfectly linear, then a passenger will have no idea of how fast they are moving and won't experience any turbulence. It's only once the airflow ceases to be linear that the turbulence will be experienced.

This is a highly simplified explanation, but it's pretty much how I understand the mechanics of flight speed.


A good way to think about it is a log in a stream.

The log is moving 0mph relative to the water around it, if there were a speed sensor on on the log the log would be recording 0mph. The water around the log would be static and in sync with the log. If you are on the bank with a radar gun, the log may be traveling 7mph relative to you, the banks, and the river bed.

If someone were to jump on the log and begin paddling, the log may move 2mph faster than the water. The log's speed sensor would show 2mph, even though relative to you standing on the shore, the log is moving 9mph.
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Colt160
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Re: Can Boeing 777-300ER go faster than speed of sound?

Thu Jun 16, 2016 2:52 am

I understand the physics on the two reply above. Again the areas of interest are : Is there such a strong jetstream that can clock 270 KTS up in hte Bering Sea? Will it be really that smooth inside a 270 KTS wind? Can the 777 fly happy and easy in such situation? From the web the fastest speed of a BA 777 was just 751 mph. This CX was once flying 953 mph / 829 KTS.....

http://www.telegraph.co.uk/news/worldne ... -time.html
 
ScottKBUF
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Re: Can Boeing 777-300ER go faster than speed of sound?

Thu Jun 16, 2016 2:53 am

Anyone actually look at the log represented in the posters' image? Shows the aircraft also executed a 180 degree turn within one minute at cruise. Pretty clear there was a glitch in the data retrieval and the aircraft was in fact not traveling at 800+kts.
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Re: Can Boeing 777-300ER go faster than speed of sound?

Thu Jun 16, 2016 2:55 am

BreninTW wrote:
Colt160 wrote:
For example, if the aircraft is doing a constant INDICATED 200 KTi (the "i" means indicated here):
Zero wind: The ground speed is 200 KT.


Simply not true, and also wrong phraseology.

To understand speeds you need to know the difference between KTAS (true airspeed in knots) and KIAS (indicated airspeed in knots). True airspeed goes up with altitude (technically speaking it is dependent on pressure and temperature, not altitude) At sea level true and indicated airspeed are the same. At high altitudes they are vastly different.

In the case from OP, the 829 knot ground speed is a flight aware glitch as it is only reported in one snapshot (happens all the time on flight aware). The rest of the flight maxes out at 586 knots, so we will use that.

At 35,000 feet and ISA temperature (roughly -55 C), Mach .85 is roughly 460 knots true airspeed. That leaves us with a 126 knot tailwind, which is common in the jetstream. At 460 knots, the INDICATED airspeed in these conditions would be 290 knots. .85/290 would be a very common cruise condition.

These figures are all based on variances in temperature and pressure altitude of course, so they true and indicated speeds could be off by several knots.
 
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Re: Can Boeing 777-300ER go faster than speed of sound?

Thu Jun 16, 2016 3:07 am

BoeingGuy wrote:
pygmalion wrote:
No it wont be fine. Max Operating Speed is .89 Mach for 7773ER. They certainly don't test it to Mach 1. The Never Exceed Speed (Vne) and Max Dive speeds are based on flutter testing and not some goal to hit mach 1.

Can the airplane survive Mach 1... not for very long and you would need to do a massive inspection afterwards since you probably damaged something as you are well into the flutter ranges. Anything .90 mach and over would require significant airframe inspections. MMO for a 772 is .87 so its even less.

And please dont bring up super critical airfoils and local mach number at some location on the wing... that is not what this is about.


I'm aware of the exact Mmo/Vmo thresholds for most Boeing models. A different way to ask this question is why did the flight test DC-8 easily survive exceeding Mach 1, yet the 777-300ER cannot?


DC8 was built and certified to "fail safe" design standards. Modern airliners like the 777 are designed to "damage tolerant" design standards. Prior airplanes were more robust but they were also heavy and very much less structurally efficient. I would also not say "easily survive". It was built hell for stout. Its controls were well balanced but heavy and in the end, it was not very flutter sensitive. Modern airliners are more sensitive to flutter and that's what really drives Vne limits. its part of what happens with the more modern supercritical airfoils
 
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Re: Can Boeing 777-300ER go faster than speed of sound?

Thu Jun 16, 2016 5:26 am

Colt160 wrote:
b747400erf wrote:
Colt160 wrote:
The speed of sound in Knots is 666.


That was your mistake.



I am not sure what you mean. But I did google it and there is no mistake.
A plane flying Mach 1.0 at sea level is flying about 1225 km/h (661 Knots, 761 mph), a plane flying Mach 1.0 at 30000 ft is flying 1091 km/h (589 knots, 678 mph) etc.


That assumes standard pressure. A 777 flying at cruise altitude is flying .83 or .84 mach. A tail wind adding to your ground speed does not count.
 
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atypical
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Re: Can Boeing 777-300ER go faster than speed of sound?

Thu Jun 16, 2016 5:48 am

trnswrld wrote:
Didn't a TWA 727 exceed the sound barrier once in a descent after some sort of issue that may have been pilot induced? Messing with flap settings to get a slightly higher cruise speed (or something I cant remember), then something went wrong and they got into a uncontrollable decent? They ended up pulling out of it, but parts of the aircraft were damaged in the process of trying to slow down and recover.


The NTSB said the plane reached an maximum of .96 mach at 31,800 feet

http://www.ntsb.gov/investigations/Acci ... AR8108.pdf Page 19, paragraph 4.

Speed of Sound

The Speed of Sound at sea level is 661 Knots but that number is inaccurate when discussing an airliner's performance because airliners never reach cruise speeds at sea level. If an airliner is going that fast at sea level then the mach number is probably way down on the list of things worrying the pilots at that moment.

At most cruise altitudes the Speed of Sound around 574 Knots. http://www.fighter-planes.com/jetmach1.htm

The speed of sound in the Earth's atmosphere is only dependent on one variable: temperature. Air density and humidity do not play any significant roles.
 
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Re: Can Boeing 777-300ER go faster than speed of sound?

Thu Jun 16, 2016 9:03 am

ScottKBUF wrote:
Anyone actually look at the log represented in the posters' image? Shows the aircraft also executed a 180 degree turn within one minute at cruise. Pretty clear there was a glitch in the data retrieval and the aircraft was in fact not traveling at 800+kts.

I for one did look at it, then sighed and decided I couldn't be bothered with making a post. The fact that your post was pretty much overlooked entirely until now should tell you why. :roll:
 
jpetekyxmd80
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Re: Can Boeing 777-300ER go faster than speed of sound?

Thu Jun 16, 2016 9:15 am

Ok, that is very obviously a flightaware inaccuracy/anomaly.
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Faro
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Re: Can Boeing 777-300ER go faster than speed of sound?

Thu Jun 16, 2016 9:32 am

Probably all modern widebody airliners -and maybe many narrowbodies too- are supersonic.

On take-off, fan blade tips go supersonic on widebody big fan engines.

It all depends on what we mean by "go faster than"...


Faro
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coolian2
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Re: Can Boeing 777-300ER go faster than speed of sound?

Thu Jun 16, 2016 9:52 am

You know, that orange KL 777 looks like it's on re-entry....
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Re: Can Boeing 777-300ER go faster than speed of sound?

Thu Jun 16, 2016 2:13 pm

Colt160 wrote:
That is still rather "spectacular". If the plane has a speed of 555 knots. The tail wind speed is 274 knots. Hurricane Katrina highest wind speed is only 150 knots. It is almost twice the Katrina..... A plane inside Double Katrina still can fly?


The difference between the jet stream and Katrina is convective activity. A hurricane has significant convective activity (up and downdrafts, thunderheads and electrical activity) and that is the main hazard, in addition to wind shear zones. A hurricane is a maelstrom, not a mass of fast-moving air.

Even in the jet stream, at the fringes both laterally and vertically there can be severe windshear and significant clear-air turbulence. But once in the fast-moving airflow, an airliner can zip along just fine.
 
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Clipper101
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Re: Can Boeing 777-300ER go faster than speed of sound?

Thu Jun 16, 2016 2:53 pm

Colt160 wrote:
The flight recorded 829 KTS (I assume it is Knot ground speed)


There is most probably a misunderstanding/mistake to the units you are quoting for speed, I can associate this figure more to (Km/h) instead of Knots (KTS). A speed of 829 Km/h can rather be associated more to a B777 flying into a headwind (not tailwind).

Talking about such things is very sensitive to units you associate the speeds you are talking to, also you need to be very careful to know what kind of speed you are talking about; putting the wrong unit, or giving the wrong reference to a speed would lead you into trouble.
 
b747400erf
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Re: Can Boeing 777-300ER go faster than speed of sound?

Fri Jun 17, 2016 6:19 am

Clipper101 wrote:
Colt160 wrote:
The flight recorded 829 KTS (I assume it is Knot ground speed)


There is most probably a misunderstanding/mistake to the units you are quoting for speed, I can associate this figure more to (Km/h) instead of Knots (KTS). A speed of 829 Km/h can rather be associated more to a B777 flying into a headwind (not tailwind).

Talking about such things is very sensitive to units you associate the speeds you are talking to, also you need to be very careful to know what kind of speed you are talking about; putting the wrong unit, or giving the wrong reference to a speed would lead you into trouble.


That high speed has been recorded on flights with large tail winds, most over the Pacific ocean. Now that I see the attached picture in the original post I did not see before, it was only recorded once so yes most likely an error.

I can't find the web site but there was one that hosted the fastest ground speed taken by pilots in the cockpit and 800-850 was recorded.
 
soectre99
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Re: Can Boeing 777-300ER go faster than speed of sound?

Fri Jun 17, 2016 7:19 am

I assume jet streams exhibit much greater velocity due to the reduced air density at those altitudes? In comparison to near sea-level hurricanes, storms, etc.

i.e. much less energy is required to propel a volume of air to those velocities
 
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Francoflier
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Re: Can Boeing 777-300ER go faster than speed of sound?

Fri Jun 17, 2016 7:39 am

Just to recap:

A 777 in normal cruise at or around optimum altitude will be clocking approx 480 kts TAS.

The 829 kts was a glitch, as a poster mentioned above, and would never happen in real life as there is no such thing as a 350kts jetstream.

The highest ground speeds a 777 (or similar) would encounter, when riding a strong jetstream across the north Atlantic or Pacific in the winter, would be in the order of 730 kts (and that would mean an exceptionally strong 250 kts jetstream).

http://www.groundspeedrecords.com/index.php
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