Max Test flight Mach Number for the 737NG!
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Max Test flight Mach Number for the 737NG!
Good evening people!
While watching this video I got curious to know what was the 737NG's max Mach number it was able to reach during its test flights.
https://www.youtube.com/watch?v=s3-g9B6Fgjs
Anybody know? Do you have info about other airliners?
While watching this video I got curious to know what was the 737NG's max Mach number it was able to reach during its test flights.
https://www.youtube.com/watch?v=s3-g9B6Fgjs
Anybody know? Do you have info about other airliners?
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Well that was wrong.
Each and every airliner (and airplane) has been tested up to VD/MD.
VD/MD are velocity dive and mach dive. They are defined in the certification standards, as the speed the airplane would reach if it started to dive (with a specific diving rate) with cruise power.
Some examples :
A320 MMO 0.82 MD 0.89
A330 MMO 0.86 MD 0.93
A380 MMO 0.89 MD 0.96
There are values for these speeds in knots as well, but not presented here.
Actually, an A320 can fly easily at M0.84-0.85, it still won't be very dangerous.
Some airlines will conduct their own "test flights" and test some features of the flight control laws.
Here is how someone can know if a speed is acceptable.
The greater the speed, the more the flight control law will pitch up the aircraft (with neutral sidestick). At M0.84, the pitch up is very slight. It will become much stronger at M0.86 or something.
One source :
?Diving? into the A320: Dive Speeds | The Flying Engineer
Each and every airliner (and airplane) has been tested up to VD/MD.
VD/MD are velocity dive and mach dive. They are defined in the certification standards, as the speed the airplane would reach if it started to dive (with a specific diving rate) with cruise power.
Some examples :
A320 MMO 0.82 MD 0.89
A330 MMO 0.86 MD 0.93
A380 MMO 0.89 MD 0.96
There are values for these speeds in knots as well, but not presented here.
Actually, an A320 can fly easily at M0.84-0.85, it still won't be very dangerous.
Some airlines will conduct their own "test flights" and test some features of the flight control laws.
Here is how someone can know if a speed is acceptable.
The greater the speed, the more the flight control law will pitch up the aircraft (with neutral sidestick). At M0.84, the pitch up is very slight. It will become much stronger at M0.86 or something.
One source :
?Diving? into the A320: Dive Speeds | The Flying Engineer
During the flight testing of the 747-8, I personally looked at flight test data between Mach 0.98 and 0.99.
No idea how hard they pushed the Max.
No idea how hard they pushed the Max.
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Tdracer : i would have liked to say the 380 was tested up to 0.99 as well but could not confirm that.
Well, one more reason why Bonin and Robert should have pushed on their stick : they did not risk anything
Well, one more reason why Bonin and Robert should have pushed on their stick : they did not risk anything
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Vmo to Vd and Mmo to Md margin
The margin between maximum operating speed (Vmo or Mmo) and dive speed (Vd or Md) is defined in the regulations involving a dive condition without pilot intervention for a number of seconds. Airplanes with overspeed protection functions in their control laws have been able to certify with less operating to dive envelope margin.
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KayPam
Aircraft type VD Kts
A350 375
A380 375
A330/340 365
A320 Family 381
How do you reconcile this statement with Airbus which says:
Crews should keep in mind that
•At high altitude, whilst it is important to always respect MMO, a slight and temporaryMach increase above that value will not lead the aircraft into an immediate hazardoussituation. At lower altitudes, exceeding VMO by a significant amount is a real threatand can dramatically affect the integrity of the aircraft’s structure.
Althoughintentional VMO/MMO exceedance cases are rare, this limit speed can typicallybe overshot when the aircraft is subject to unusual wind and/or temperaturegradient. Prevention is therefore essential.
VMO/MMO IN A NUTSHELL
VMO/MMO is the “never TO exceed” speed
Aircraft type VD Kts
A350 375
A380 375
A330/340 365
A320 Family 381
Actually, an A320 can fly easily at M0.84-0.85, it still won't be very dangerous
Crews should keep in mind that
•At high altitude, whilst it is important to always respect MMO, a slight and temporaryMach increase above that value will not lead the aircraft into an immediate hazardoussituation. At lower altitudes, exceeding VMO by a significant amount is a real threatand can dramatically affect the integrity of the aircraft’s structure.
Althoughintentional VMO/MMO exceedance cases are rare, this limit speed can typicallybe overshot when the aircraft is subject to unusual wind and/or temperaturegradient. Prevention is therefore essential.
VMO/MMO IN A NUTSHELL
VMO/MMO is the “never TO exceed” speed
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Easyjet flew a 737NG at 447 kts by accident. No damage was found to the aircraft. I'm sure you can dig up the investigation report on google.
*Edit, there you go: https://assets.publishing.service.go...EZJK_09-10.pdf
Personally, I have once flow 0.86 during a severe shift of 100 knots cruise winds. With thrust at idle and speed brakes extended the speed just kept going up. Otherwise, it was completely uneventful.
These things are built like tanks.
*Edit, there you go: https://assets.publishing.service.go...EZJK_09-10.pdf
Personally, I have once flow 0.86 during a severe shift of 100 knots cruise winds. With thrust at idle and speed brakes extended the speed just kept going up. Otherwise, it was completely uneventful.
These things are built like tanks.
These things are built like tanks.
Exceeding the published Vmo or Mmo by a small amount eats into the rather small margin between the published operational limit and the flight test demonstrated limit. The flight test demonstrated dive speed was established on a new airplane by the way. There's really no guarantee that aeroelastic or structural limits won't be reached at less than Vd or at a lesser load factor than was found acceptable during testing. Since a line pilot has no way of knowing which test conditions may have been found to be speed limiting during flight tests, there is no way to know which deleterious effect will be encountered first above the limiting speed.
While a number of older part 25 jets have flown well beyond established airspeed limits during certain incidents occurring in line service, many of these resulted in serious damage or control difficulties. Or sometimes much worse.
Nor would I count on newer airplanes to be built with the same level of "over engineering" as older types either. So all things considered, I wouldn't prefer to deliberately exceed published Vmo/Mmo unless it were somehow a better option than the available alternatives. In all likelihood it'll stay together and remain controllable up to the speed the test pilots took it to. Why would I want to take the airplane out into a flight regime the test pilots didn't?
At some point most jet pilots will inadvertently exceed Mmo when encountering certain unforeseen atmospheric conditions. Most commonly during descent into colder air or increasing headwind component. Because a margin of between .05 to .07M exists Between Mmo and Mdf, no structural damage or loss of controllability should occur during a minor exceedence. In some types this may be getting very close to real trouble. Others may provide a more generous margin than strictly required. A number of aircraft have been lost during flight test while exploring the corners of the speed envelope.
Until some some kind soul offers to pay my way through test pilot school, I'll just stick to the limits established by the trained and qualified test pilots who conducted the certification tests. Why do otherwise?
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Vilas, from the Airbus Safety First #21
Given this, I think KayPam might be right.
Page 13 for anyone interested !
How is VMO/MMO determined?
VMO/MMO is established with regards to the aircraft’s structural limits and it provides a margin to the design limit speed/Mach number VD/MD. VD/MD must be suf ciently above VMO/MMO to make it highly improbable that VD/ MD will be inadvertently exceeded in commercial operations. Several certi cation criteria exist. As a result, on Airbus aircraft, MD is usually equal to MMO + 0.07 and VD approximately equal to VMO + 35 kt.
The applicable VMO/MMO are indicated in each Aircraft Flight Manual. For example, VMO/MMO and VD/MD are given in the following table.
VMO/MMO is established with regards to the aircraft’s structural limits and it provides a margin to the design limit speed/Mach number VD/MD. VD/MD must be suf ciently above VMO/MMO to make it highly improbable that VD/ MD will be inadvertently exceeded in commercial operations. Several certi cation criteria exist. As a result, on Airbus aircraft, MD is usually equal to MMO + 0.07 and VD approximately equal to VMO + 35 kt.
The applicable VMO/MMO are indicated in each Aircraft Flight Manual. For example, VMO/MMO and VD/MD are given in the following table.
Page 13 for anyone interested !
vilas,
Big difference between inflight air loads and overloads that an aircraft structure is optimized and designed for vs actual impact to the airframe in an off runway excursion.
Personally I do believe Boeings are built like 'tanks of the air' their strength has been proven time after time in decades of service (in some quite incredible events far outside the certified flight envelope) and i've never seen a paragraph in any Boeing flight manual warning me that structural failure may occur if I exceeded VMO / MMO
Big difference between inflight air loads and overloads that an aircraft structure is optimized and designed for vs actual impact to the airframe in an off runway excursion.
Personally I do believe Boeings are built like 'tanks of the air' their strength has been proven time after time in decades of service (in some quite incredible events far outside the certified flight envelope) and i've never seen a paragraph in any Boeing flight manual warning me that structural failure may occur if I exceeded VMO / MMO
We won't talk about DC-8s.
Ok, we will.
History, Travel, Arts, Science, People, Places | Air & Space Magazine
Ok, we will.
History, Travel, Arts, Science, People, Places | Air & Space Magazine
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Valmont, stilton
What I quoted is exactly from the same issue of Safety first page 15. I don't know how did you miss what is written in bold letters. There is a difference between occasional speed excursion caused by environmental factors beyond control and deliberately doing it for a sustained period of time. The manufacturer has given you VMO/MMO. They don't have to tell you anything more. If they had your confidence wouldn't they increase the VMO/MMO figures? Commercial aircrafts are not combat aircrafts. Built like tanks is a very non professional lay man like statement. Nobody builds them even a bit more stronger than required because it adds to weight which reduces payload and increase fuel consumption.
Yah, But Sully's airbus didn't brake up despite him dropping speed considerably but 737NG broke up in Bali. You are advised to see the documentary made by Al Jazeera on Boeing especially 737NG.
What I quoted is exactly from the same issue of Safety first page 15. I don't know how did you miss what is written in bold letters. There is a difference between occasional speed excursion caused by environmental factors beyond control and deliberately doing it for a sustained period of time. The manufacturer has given you VMO/MMO. They don't have to tell you anything more. If they had your confidence wouldn't they increase the VMO/MMO figures? Commercial aircrafts are not combat aircrafts. Built like tanks is a very non professional lay man like statement. Nobody builds them even a bit more stronger than required because it adds to weight which reduces payload and increase fuel consumption.
Big difference between inflight air loads and overloads that an aircraft structure is optimized and designed for vs actual impact to the airframe in an off runway excursion.
Last edited by vilas; 26th Oct 2016 at 14:25.
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Many consierations for airplane structural design
There are many factors that go into designing airplane structure. Two basic issues are strength and fatigue. This is particularly an issue for aluminum wings. For many portions of an aluminum wing fatigue is the designing factor. Those sections must be thick enough to resist developing fatigue cracks and to reduce the growth rate for any small cracks that do form. Given enough material to meet fatigue requirements, that portion of structure may be able to withstand loads associated with speeds well beyond Vd/Md.
An interesting change in design practice has come about with the use of composite materials. Composites have much less tendency to fatigue and thus design with these materials is driven more by maneuver and ultimate gust loads. An important result is that structures can be build with less material and there is design incentive to reduce maneuver loads as that allows for further reduction in the structural gauges. A fallout of all of this is that an older model with primarily aluminum structure may be more tolerant of increased loads associated with exceeding Vd/Md than a newer model built with composite materials.
The bottom line is that airplanes should be operated at/below Vmo/Mmo so that inadvertant exceedences of Vd/Md are highly unlikely.
An interesting change in design practice has come about with the use of composite materials. Composites have much less tendency to fatigue and thus design with these materials is driven more by maneuver and ultimate gust loads. An important result is that structures can be build with less material and there is design incentive to reduce maneuver loads as that allows for further reduction in the structural gauges. A fallout of all of this is that an older model with primarily aluminum structure may be more tolerant of increased loads associated with exceeding Vd/Md than a newer model built with composite materials.
The bottom line is that airplanes should be operated at/below Vmo/Mmo so that inadvertant exceedences of Vd/Md are highly unlikely.
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Vilas : VD and MD are two different things (obviously).
If you were to fly faster than MD at a low altitude, you would be way past VD, and the impact pressure would damage your aircraft or even destroy it
So yes, you can fly at a high altitude at MMO+0.03 without a problem, that's because the problems caused by a high mach number with a low VD are different than those caused by a high impact pressure.
However, the incident cited in a previous message with a 737 NG at a low altitude reaching 430kt proves that there is still a quite large* margin behind VMO/MMO
*Please don't overinterpret this "quite large". A quite large mach excursion in my mind would be a quarter of the difference between max operating and dive speeds.
Please also do not consider my messages as an encouragement to fly past VMO/MMO
Even more so on a regular basis.
I am just saying that you should not panick if your aircraft were to exceed VMAX by a bit.
VMAX includes VFE, which also has a margin before slats/flaps destruction. Slats and flaps should jam before breaking.
In my airclub, a pilot anonymously reported exceeding the VFE by about 15kt on a light aircraft, during a few minutes. The plane was inspected and nothing was found.
This is all thanks to the 50% margin that airplane makers have to guarantee, between the maximum autorized ("legal") load and the load that will actually break the airplane.
If you were to fly faster than MD at a low altitude, you would be way past VD, and the impact pressure would damage your aircraft or even destroy it
So yes, you can fly at a high altitude at MMO+0.03 without a problem, that's because the problems caused by a high mach number with a low VD are different than those caused by a high impact pressure.
However, the incident cited in a previous message with a 737 NG at a low altitude reaching 430kt proves that there is still a quite large* margin behind VMO/MMO
*Please don't overinterpret this "quite large". A quite large mach excursion in my mind would be a quarter of the difference between max operating and dive speeds.
Please also do not consider my messages as an encouragement to fly past VMO/MMO
Even more so on a regular basis.
I am just saying that you should not panick if your aircraft were to exceed VMAX by a bit.
VMAX includes VFE, which also has a margin before slats/flaps destruction. Slats and flaps should jam before breaking.
In my airclub, a pilot anonymously reported exceeding the VFE by about 15kt on a light aircraft, during a few minutes. The plane was inspected and nothing was found.
This is all thanks to the 50% margin that airplane makers have to guarantee, between the maximum autorized ("legal") load and the load that will actually break the airplane.
Last edited by KayPam; 27th Oct 2016 at 23:57.
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perhaps the cockpit hump had an 'area rule' effect ( less drag ) at near supersonic speeds ??
Supposedly, when they extended the upper deck for the 747-300/400, the improvement in area rule effectively cancelled the increase in weight of the extra structure.