Aircraft speed
 

It seems to me that certain airlines fly much slower than others and certain aircraft fly much slower than others.

By way of example I follow Jet2 flights on flightradar24 to ensure I do not spend too much time waiting for family at the airport when I collect them. Jet2 planes never seem to get above 500mph at most whereas most other airlines seem to go well over than speed.

However when flying I always get the impression that flights with Boeing aircraft are quicker than Airbus and the in-flight entertainment system seems to bear this out.

Once I watched a Jet2 B757 take off from MAN after being delayed by 90 minutes. Behind it was a Lufthansa A320 to FRA. The pilot seemed to be giving it the beans as he flew at 620mph all the way from just after take off to well over the Balkans as if to catch up for lost time and avoid the LH hitting the back of him.

Am I right?

Have you taken account of the wind? If there is a 50 kts wind and an aircraft is flying into it, it's groundspeed will be reduced by 50 kts. On the other hand, flying the opposite way will add 50 kts. This means that two identical aircraft flying at the same airspeed will have groundspeeds 100 kts different. I suspect that the programme you are using indicates groundspeed.

I know it's a while since I retired but I doubt that any civil aircraft would file an airspeed of "620 mph" and aircraft don't fly fast to stop the one behind hitting it!!!!

I think you need to read a few books on aviation...

Airlines operated their aircraft using something called a cost index. This is a figure tapped into the aircraft FMC to determine how efficiently the aircraft operates. Generally a low cost index will mean lower speeds. Jet2 do have a reputation for using a very low cost index, I think Flybe do also. Fuel is obviously very expensive at the moment and the less you can use the better I guess.

Espada - in the UK we are trained NEVER to let the Luftwaffe (sorry, Lufthansa) get behind us (or in the sun).

Aircraft often do fly 'faster' to prevent the one behind getting in the way - it is often requested by ATC.

'620' mph is a touch fast, though! It is just below the speed of sound and not likely.

Something I have always wondered is: does the flight's distance and duration affect the cruise speed in any one particular aircraft? In other words, do you cruise slower on shorter flights?

For example, if you fly from London to Manchester in an A320, would you cruise at a slower speed than, say on an A320 flight from London to Athens in order not to arrive too quickly and in order to 'drag out' (no pun intended) the length of the cruise?

As explained above, I appreciate that speeds also vary depending on external factors, such as ATC requests.

The "Cruise Mach Number" for any given type of aircraft can be significantly different.

The B747 generally cruises at .83 Mach whereas the Airbus family of aircraft cruise at a significantly lower Mach Number. I'm guessing at around .76 (someone will correct me I'm sure).

Prepare to be corrected! The Airbus "family" is huge and varies from the A318 to the A380. At normal cruise altitudes, the A320/A321 will cruise at about M.78 whilst the A380 will be somewhere towards M.85.

The assumption that Boeings are faster than Airbuses simply isn't true and is a huge generalisation. The B737-200 for example flies (flew) at M.72, the 737-300 IIRC is M.75, both slower than airbus narrow body aircraft which in turn are slower than most widebody aircraft.

It's all about fuel these days not racing around trying to shave 2 minutes off a flight!

Unless that means that you make it before closing time.

Espada, some of Jet2's fleet are old 300 clunkers that cruise around at .73ish.

BOAC, 620mph is only 540kts, not unheard of with a decent tailwind, granted it won't be quite as good on the way back. Assuming he's looking at GS!

Thanks all.

I think the flightradar24 website gives speed in kts and mph and assume that mph will be ground speed.

Yes the Jet2 planes appear to be old clunkers! (at least the ones I have flown on). They give the impression of being held together with silicone mastic like you seal a bathroom with.....

<<I think the flightradar24 website gives speed in kts and mph and assume that mph will be ground speed. >>

Whether you choose mph or kts I'm 99% certain that what you see is groundspeed.

Slightly off topic - can't remember where I read the physics of it (possibly Barry Schiff) but do pilots INCREASE their cruise speed when flying with a headwind, and conversely decrease it when flying with a tailwind?

I appreciate certain sectors (NAT tracks for example) where Mach number is part of the clearance and cannot really be altered (?) but I seem to remember it was about trying to maximise the positive effects of a tailwind (and minimise the negatives of a headwind) with regards to total fuel consumption.

Just wondered if this actually occurred?

dany - the 'software' in an FMS does that automatically if used. Based on the old principle that with a cruise speed of 200kts in a 200kt headwind it takes a while to get anywhere.:)

So is the answer to my question: 'no difference' ? :hmm:

What a load of cr@p, and no it's not just because I fly them. They're no older than many other aircraft knocking around in Monarch, Thomas Cook, Thomson etc. and they spend less time airborne, therefore more time on the ground getting some TLC. You won't find many yellow stickers in a Jet2 cockpit.:ok:

In answer to the original question, looking at where you watched the aircraft going, I imagine it was a loooong duty day:{. they might well have been delayed departing:*, and therefore been tight on hours to get the job done. Increase the speed round trip, make up 30 mins or so, and hey presto, no tech stop with a fresh crew to pick up the last leg of the journey required:D.

- sorry - I assumed someone would jump in.

In essence no - there may be a difference. Because sectors are shorter, the cruise speed may well be slower particularly if the cruise level is lower eg MAN-LGW always used to be at FL190. It is not normal for airlines to slow down on short sectors (rarely we did in DanAir on the LGW-CDG when we had 60+ business class pax enjoying our excellent service) but it can give the c/crew a bit more time to attend to the important people - you know, the ones who pay our salaries!:)

Thank you chaps.

"What a load of cr@p, and no it's not just because I fly them. They're no older than many other aircraft knocking around in Monarch, Thomas Cook, Thomson etc. and they spend less time airborne, therefore more time on the ground getting some TLC. You won't find many yellow stickers in a Jet2 cockpit."

They may be no older than other UK charter aircraft, but compared to what I usually fly in (Swiss or LH), they are sheds. You can see where the TV screens have been removed and blanked off in a very crude fashion. And usually if you look at what you get for your money on the full service airlines they are not that much more expensive.

My "point" was that different aircraft fly at different cruise Mach No, NOT to denegrate any particular breed of aeroplane.

Certainly, in my early days of flying, the A310/A320 were significantly slower than the L1011/B747 and that we would have to slow down because of a slower Airbus up ahead.

Typical PPrune... someone else "wading-in" with a "gripe" about what another poster might have inferred :ugh:

The Jet2 737-300s I flew in to and from Rome last summer were very tired looking aircraft. I got a good look at the exterior as we walked from the airbidge to the aircraft in the rain (love that low cost service!) and I wasn't impressed.

Speeds can vary for many reasons. We quite often bump up the cost index to make our arrival time - which makes commercial sense if there are connections which would be costly to the company if they aren't made. Also, I remember slowing long haul trips back to right down not to arrive during the curfew and incur a heavy increase in landing fees.

Both the B737-300 and B757-200 that Jet 2 use are some of the oldest around and the average fleet age is greater than most other UK airlines. However, this doesn't imply a poor aircraft as maintenance is the key issue. The problem is passengers will only base their opinions on how shiny the a/c looks and how good the interior is. Ask any of my friends and they'll say most of the Jet 2 fleet is 'past it' - fair or not.