Is there a speed limit on planes?

ardinn

Sitting here in the aiport an hr delayed because the plane im going on arrived late! Do planes have a speed limit? If the planes late can captain careful not 'drive er on' so to speak. Put the foot down ye spa I have a session in Portugal thats waiting on me!!!

Amirani

Nah not really. Flying faster uses more fuel though, and fuel is the largest variable cost to commercial airlines.

Donald Trump

I think you are allowed two wraps per passenger

McMurphy

ardinn wrote: »

Sitting here in the aiport an hr delayed because the plane im going on arrived late! Do planes have a speed limit? If the planes late can captain careful not 'drive er on' so to speak. Put the foot down ye spa I have a session in Portugal thats waiting on me!!!

There's definitely one on descending anyway.

Go hard enough over it, and your bolloxed.

Samuel T. Cogley

ardinn wrote: »

Sitting here in the aiport an hr delayed because the plane im going on arrived late! Do planes have a speed limit? If the planes late can captain careful not 'drive er on' so to speak. Put the foot down ye spa I have a session in Portugal thats waiting on me!!!

Air traffic control can set limits where needed, my only knowledge of this being watching 'Pushing Tin'.

TheValeyard

Go to slow and plane goes bye bye

EchoIndia

This is a good explanation: https://www.cntraveler.com/story/how-pilots-make-up-time-in-the-air

nowaynever

Yes, terminal velocity.

SEPT 23 1989

i would be more worried about the violent thunderstorms you will be flying into tonight

DMcL1971

Planes fly along specific routes. If you fly too fast you will catch up the plane ahead of you on that route. So you have to stay at a specific speed.

odyssey06

If you put one on the M1, yes.

And, presumably, on the runway.

Supersonic military aircraft are probably limited in where they can go BOOM. Think Concorde could only go supersonic over the Atlantic.

AllForIt

Depends how big your rectum is.

Donald Trump

Amirani wrote: »

Nah not really. Flying faster uses more fuel though, and fuel is the largest variable cost to commercial airlines.

Yeah but but but, if you fly fast enough you can get there before the fuel runs out!

Roger_007

Donald Trump wrote: »

Yeah but but but, if you fly fast enough you can get there before the fuel runs out!

Genius.:D:D

prinzeugen

ardinn wrote: »

Sitting here in the aiport an hr delayed because the plane im going on arrived late! Do planes have a speed limit? If the planes late can captain careful not 'drive er on' so to speak. Put the foot down ye spa I have a session in Portugal thats waiting on me!!!

Yes. And in addition to the corridor thing, the max speed varies depending on how high the plane is flying.

A standard civil airliner cannot go faster than the speed of sound (Mach 1) but would cruise at around Mach 0.90 (90% of the speed of sound)

The speed of sound at sea level is about 760mph and at 20,000ft is about 705mph.

So the higher a plane flies, its max speed in mph will drop.

For example a 747 at sea level could do a max of about 730mph while one at 20,000ft would have a max speed of about 685mph.

However at high altitude, the air is thinner meaning the plane uses less fuel which is why long distance flights fly at 38-40,000 ft. Money.

cml387

The limit for a passenger aircraft is the speed of sound. Exceed that and bad things happen.

Car99

Yes, though to a very limited extent. Pilots almost never do the in-flight equivalent of foot to the floor. Each commercial jet has a Flight Management System (FMS) that calculates its most efficient air speed given certain variables such as the number of passengers aboard and the cruising altitude. If a pilot wanted to accelerate past this sweet spot of efficiency, even by a little bit, he could end up burning substantially more fuel and adding thousands of yoyo's to the overall flight expense. So while it’s theoretically possible for a pilot to floor it, that only happens under special circumstances, almost always under direction from a superior, such as when air traffic control needs to clear up a scheduling conflict.

Or a good tail wind will help and save the JetA1.

Hammer89

DMcL1971 wrote: »

Planes fly along specific routes. If you fly too fast you will catch up the plane ahead of you on that route. So you have to stay at a specific speed.

If a plane is too close to the one ahead does it stop for five minutes like the Dart?

Del2005

Car99 wrote: »

Yes, though to a very limited extent. Pilots almost never do the in-flight equivalent of foot to the floor. Each commercial jet has a Flight Management System (FMS) that calculates its most efficient air speed given certain variables such as the number of passengers aboard and the cruising altitude. If a pilot wanted to accelerate past this sweet spot of efficiency, even by a little bit, he could end up burning substantially more fuel and adding thousands of yoyo's to the overall flight expense. So while it’s theoretically possible for a pilot to floor it, that only happens under special circumstances, almost always under direction from a superior, such as when air traffic control needs to clear up a scheduling conflict.

Or a good tail wind will help and save the JetA1.

They also put the foot down if they have a lot of transfer passengers on board, fuel costs less than hotels.

Comhrá

Aircraft have a VNE (Never exceed speed) If they fly faster, they risk doing structural damage to the airframe. Flaps, ailerons, even the tail or wing structure may break off causing catastrophic results.

DMcL1971

Hammer89 wrote: »

If a plane is too close to the one ahead does it stop for five minutes like the Dart?

Absolutely, it pulls in to a lay by, or a sky by as it is known and hovers for a few minutes.

dxhound2005

Flights across the Atlantic have to report to ATC at certain waypoints, including their airspeed (Mach number). They have to give their ETA at the next waypoint.

prinzeugen

So many early jet pilots were killed because they looked at the airspeed meter and not the mach meter.

Once airborne, mach speed not knots or mph is all that matters at altitude.

somefeen

prinzeugen wrote: »

So many early jet pilots were killed because they looked at the airspeed meter and not the mach meter.

Once airborne, mach speed not knots or mph is all that matters at altitude.

Can you elaborate?
I know this isn't the aviation forum but...

I thought Mach was airspeed just expressed as percentage of the speed of sound.
I thought they would both be measured the same way with the same instruments, just expressed differently.
Do you need to calculate Mach as s function of indicated airspeed and altitude?
Do airspeed indicators under/over read at high altitudes or something?

cnocbui

DMcL1971 wrote: »

Planes fly along specific routes. If you fly too fast you will catch up the plane ahead of you on that route. So you have to stay at a specific speed.

A week or so ago I watched two planes overhead, with the larger one rapidly catching up to the smaller one and then overhauling it smartly. They were probably on slightly different flight levels but they were still physically very close.

Overheal

Amirani wrote: »

Nah not really. Flying faster uses more fuel though, and fuel is the largest variable cost to commercial airlines.

Power = Energy / Time. Fuel is a finite energy source.

There are of course speed limits however in most cases: https://www.flyingmag.com/aircraft-speed-limits-explained

prinzeugen

somefeen wrote: »

Can you elaborate?
I know this isn't the aviation forum but...

I thought Mach was airspeed just expressed as percentage of the speed of sound.
I thought they would both be measured the same way with the same instruments, just expressed differently.
Do you need to calculate Mach as s function of indicated airspeed and altitude?
Do airspeed indicators under/over read at high altitudes or something?

Mach (or the speed of sound) changes with altitude and humidity.

The basics are a few posts back.

A plane will show airspeed and mach. You always look at mach once you are in the air.

Early pilots that had converted from Spitfires to jets were use to looking at airspeed.

Jets flew higher and faster so plenty lost control at altitude going too fast or lost control at low level by going too slow.

Its to do with lift from the wings and overspeed damage.

No ejection seats in those days so many were cut in two by the tailplane when they bailed out with just a parachute.

Early jets took a while to speed up and once a pilot realised they were too slow, it was too late. The plane would stall and hit the ground before the engines got to full power.

Rented Mule

Everyone seems to be missing the point of this thread.

If you take a step back it becomes much clearer.

This is a thinly veiled "Look at me!! I'm on my way to Portugal" thread.

somefeen

Rented Mule wrote: »

Everyone seems to be missing the point of this thread.

If you take a step back it becomes much clearer.

This is a thinly veiled "Look at me!! I'm on my way to Portugal" thread.

I think we should all be dissapointed with ourselves. Its taken two pages and a few brief discussions on aerodynamics before anyone used the 'thinly veiled' meme.

What happened to you, after hours?

Sam Quentin

ardinn wrote: »

Sitting here in the aiport an hr delayed because the plane im going on arrived late! Do planes have a speed limit? If the planes late can captain careful not 'drive er on' so to speak. Put the foot down ye spa I have a session in Portugal thats waiting on me!!!

I fly a fair bit, I DONT LIKE IT.
Anyway my only knowledge of speed limits on aircrafts is........
The time the pilot broadcast:- It's a beautiful evening in Dublin, we should see the west coast of Ireland in 1hr, we have a 300mph tail wind guiding us... I dont know what he said after that :eek:

smurfjed

There are multiple limits, some are based on the aircraft itself such as VMO/MMO, these are how fast the aircraft is designed to fly and may be significantly higher than the economical speed which they usually fly at, so a pilot may increase the speed above the economical speed if he has a good reason.

Then there are airspace restricted speeds that are general 250 kts and 200 kts, or specific to an published arrival or departure procedure where it will say may speed XXXX.

Then there are ATC restrictions based on traffic flow patterns, where they can tell an aircraft to speed up or slow down at specific points.

So as usual in aviation, there are multiple answers to your question

smurfjed

A standard civil airliner cannot go faster than the speed of sound (Mach 1) but would cruise at around Mach 0.90 (90% of the speed of sound)

Which modern airliner flies at M.90?

smurfjed

Oops, I forgot speed limits due to turbulence.

Mellor

smurfjed wrote: »

Which modern airliner flies at M.90?

747 spec sheet from FAA says MMO of M.92

http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgMakeModel.nsf/0/29f8f1f15b2b08b786257479004b50e1/$FILE/A20WE.pdf

AndyBoBandy

Yes.

Below 10,000 feet planes are limited to 250 knots.

CalamariFritti

There are set speed limits. Below 10,000 foot its typically 250 knots. Mostly for safety and air traffic control reasons.

A plane's speed is measured in airspeed as in how fast does the plane travel through the air. Its unit is knots like at sea. Thats because the medium they're travelling in (air or water) may move itself (wind or current) or has other variables like pressure or temperature. So the unit is relative to the medium you're travelling in which is not the same as moving your finger over a map (ground speed) if you know what I mean. Also as the air gets thinner in higher altitudes (pressure again) the same airspeed translates into a faster ground speed the higher up you are. So there are two types of airspeed (knots). Airspeed at ground level and 'true' air speed which brings the altitude into it.
Just as an example a Boeing 737 has a max true air speed in the high 400s. It cannot go faster or else it would be (very) unsafe.

Anyway, airliners are travelling at the most economical speed, best altitude with best speed at relatively lowest fuel consumption. But its not a huge amount away from their max airspeed so really they cannot put their foot down much or at all. It is what it is.

Sometimes you get lucky and the wind blows into the direction you're going so you get little help added to your ground speed. Sometimes its the other way around.

smurfjed

747 spec sheet from FAA says MMO of M.92

Design speed, we have operated the B747-SP/100/200/300/400/8F and they range from M.83-.86, the fastest that i have heard of a light weight B744 was M.88, before it ran out of thrust.

VMO is different as it usually involves descent and has gravity involved.

smurfjed

Yes.
Below 10,000 feet planes are limited to 250 knots.

Which can be exceeded.

Corcaigh84

https://www.youtube.com/watch?v=n1QEj09Pe6k&feature=youtu.be

Roger_007

Why are knots, (nautical mph), still used in aviation?
Why don't they standardise groundspeed and airspeed measurement to kph only?

AndyBoBandy

Roger_007 wrote: »

Why are knots, (nautical mph), still used in aviation?
Why don't they standardise groundspeed and airspeed measurement to kph only?

As a previous poster said knots are variable, as the medium you are traveling through is liable to change (wind blowing, tides flowing)

Mph & kph are related to something static, knots are related to the water or air which you are moving through, which can also move!!

Samuel T. Cogley

AndyBoBandy wrote: »

As a previous poster said knots are variable, as the medium you are traveling through is liable to change (wind blowing, tides flowing)

Mph & kph are related to something static, knots are related to the water or air which you are moving through, which can also move!!

Err... not really :pac: a knot is 1.852 Kmph

Knots are used as they translate better to degrees and minutes in navigation.

ygolometsipe

Garda definitely have speed cameras in the clouds

Roger_007

AndyBoBandy wrote: »

As a previous poster said knots are variable, as the medium you are traveling through is liable to change (wind blowing, tides flowing)

Mph & kph are related to something static, knots are related to the water or air which you are moving through, which can also move!!

I don't understand any of that.
A knot is always equal to 1.852kph. It doesn't vary no matter what medium you are travelling through.
Any speed can be expressed in knots, mph or kph.
I was simply wondering why unit of knots is still being used at all.

The One Doctor

ardinn wrote: »

Sitting here in the aiport an hr delayed because the plane im going on arrived late! Do planes have a speed limit? If the planes late can captain careful not 'drive er on' so to speak. Put the foot down ye spa I have a session in Portugal thats waiting on me!!!

Speed limit (under 10000ft) is 250knots, or about 435kph. Above that, the speed limit is just under the speed of sound for civil aircraft (over land).

It always makes me laugh to see idiots with fast cars. On the ground the speed limit is 120kph. Go just 50 feet into the air and the speed limit is 435kph.

The idiots should spend their money on planes, not pissy little cars.

Samuel T. Cogley

Roger_007 wrote: »

I don't understand any of that.
A knot is always equal to 1.852kph. It doesn't vary no matter what medium you are travelling through.
Any speed can be expressed in knots, mph or kph.
I was simply wondering why unit of knots is still being used at all.

If you use any sort of large scale chart 1000 KMs isn't the same distance on the chart at the top as it is the bottom. Google a Mercator Projection and a Peters Projection and look how different the world looks.

Capt'n Midnight

Roger_007 wrote: »

Why are knots, (nautical mph), still used in aviation?
Why don't they standardise groundspeed and airspeed measurement to kph only?

It's a hangover from navigation. At the equator then you travel 1 nautical mile you have moved by 1/60th of a degree.

Aircraft do speed limits set by traffic and others set by design.

Most aircraft have a "do not exceed" speed. Because bad stuff happens like wings getting ripped off.

The sound barrier was considered a speed limit but passenger airliners like the DC8 and VC-10 have gone through it in shallow dives.


Most commercial jets with swept back wings would be optimised for between 80%-95% of the speed of sound, faster and it takes too much energy and too noisy. Slower and you can't do as many flights so you need more planes and crew to move the same amount of passengers.

Flying high means less air resistance so less fuel on longer flights but you need to climb up there and you need to go fast to stay aloft in the thin air.


Planes with straight wings and propellers are more economic but about half the speed of the ones above so good for shorter distances.



The other speed limit of planes is when they go too slow and stall, and could fall right out of the sky just like something with a Capissen 38 Mark II engine .

The early versions of the U2 spy plane flew so high that the air was so thin that they could be built like sailplanes / gliders even though they were flying close to the speed of sound. When turning at the flight envelope the plane could start to shake, one wingtip going through the sound barrier, and the other stalliing. So both limits at the same time.


Other speed limits are the thermal thicket just above Mach 2 where the planes get so hot that aluminium starts to weaken. Which is why the SR-71 and XB-70 had lots of titanium. The Mig-25 used lots of steel which meant it had to have a lot of thrust to keep it in the air, so there was no problem powering it's 600KW radar, which unlike mobile phone masts was a serious health risk to anything in it's path.