727 vs 747 cruise speeds

[G-ALAN]

Is it true the 727 can cruise at M.902? I ask because people keep telling me the 747-400 is the fastest airliner (besides Concorde) with a cruise speed of M.86, yet I've read from various sources that the 727 has a max cruise speed of M.902

Thanx for any help

[GlueBall]

727? Only in a dive!
However, the Convair 990 could cruise at M.90, if you had full tanks and weren't going too far.

The Convair 880 was fast too: 880 feet per second.

[747FOCAL]

G-Alan,

Actually, the 727 was designed to cruise at M.92 originally. When the gas crunch of the 70s hit everybody throttled them back.

Glueball,

I have original flight test video of the 727 with Boeing's chase plane shot from another plane cruising at M.965. Thats level cruise not a dive.

Due mostly to the large amount of 727s built, the 727 has the most incidents of exceeding mach of any other aircraft ever built that was not designed to break the sound barrier.

[G-ALAN]

M.92! a pretty fast aircraft for it's day then! What I don't understand then is what all the hype was about when Boeing announced its failed Sonic Cruiser. They were saying things like this will set new standards for aircraft travel, they were going on as if flying an airliner around M.9 was something new. They already built a bloody aircraft 40 years earlier which was in the same legue, well speed wise anyway.

[JJflyer]

Cruising

G-ALAN

The Sonic Cruiser was supposed to do the high speed cruise economically where older generation fast commercial aircraft did not.
Cruising at .84M with the old threeholer will gulp fuel faster than you dare to watch. Don't even want to think what the fuel flows would be at speeds higher than that. Quite thirsty the old girl, but slippery.

None of the "New" generation Boeings from B757 onwards or any of the Airbus products where designed for speed, rather for lower fuel consumption.

B747 FOCAL. Yip either the B727 or B747 with new engines and some other refinements would make a good Sonic "Snoozer" alternative.

Cheers

JJ

Edited for typos etc

[747FOCAL]

G-Alan,


Ahhhhh, now you are touching on the beauty of Boeing and why they are slowly slipping into the Abyss.


There is nothing left of the original Boeing team that developed the 727 or the 747. Everybody that is left is either to nieve from lack of work experience or completely stupid. For less than half what the projected design and build costs of the Sonic Loser they could have had a re-engined(to meet noise and NOX regulations) varient of the 727 that would have cruised at .92 or above and not use to much petrol.

[G-ALAN]

I see! I guess it was all just a competition thing with airbus, they build a big aircraft so Boeing build a fast aircraft, they build a very long range aircraft so Boeing build an even longer range aircraft etc.

It would be nice to see an old bird like a 727 re-engined and modified to fly for another 20 years or so. I'm sure quite alot of the current operators would be very interested in this. Anyway it ain't gonna happen unless those folks at Boeing get their heads screwed on properly

[Intruder]

Was that "max cruise speed" of .902 for the 727 a cruise speed or MMO (Mach -- Max Operating)? If MMO, the 747-400 has a MMO of .92 (.90 in RVSM airspace) for comparison. It cruises normally at .84-.86, though.

[Flight Detent]

INTRUDER,

yeah, just like the B747-100 & 200 & 300 & SP!

but with class!!

Cheers

[18-Wheeler]

The 727's were typically run at 0.80 to 0.82.
747's run from 0.84 for the -100's up to 0.86 for the -400's.
I believe the fastest production airliner after the Concorde is the Tupolev Tu-154, which can cruise at 0.97, IF you can stand the fuel flow!

[steamchicken]

What of the VC10?

BEagle
Over 2500 posts and I think it's obvious this is going to be my Personal Title. Hey, PPRuNe is free isn't it?
posted 1st April 2002 11:05
--------------------------------------------------------------------------------

In the past I've cruised across the Pond at M.88 indicated, but such things are no longer permitted. Cruising for optimum payload availability is the holy grail nowadays - and Mno is .866 indicated.

I'm authorised to take the old ladies briefly up to over .9 IMN on air tests, but I recover long before Mne of .94 IMN is reached - and they certainly won't do that in level flight! As for M1.2....err, no. Not possible!


[Last edited by BEagle on 1st April 2002 at 11:18]

[TopBunk]

From a Boeing fan to you Boeing guys:

please realise that aside from anything else Boeing's BIG problem is the incompatibility of their range.

B717 (well MD95), B737, B757/767, B777, B747-400: no (or v.limited) cross crew qualification capability.

Airbus A318/319/320/321/330/340/380 - standard philosophy, 2 or 3 day for an additional type-rating, that's it!

Now if you were an airline CEO, with a mix of short and medium and longhaul ops, what would you equip you airline with?

..... no bl**dy decision really.

Tough, but that's where it's at, to a CEO whether it cruises at M0.88 or M0.84, they don't care, it's all about fuel burn and max flexibility.

[G-ALAN]

Intruder: .902 is max cruise speed according to a book I read on the 727, I don't know how accurate it was though because, like 747FOCAL says, and what I have read in some other books it can cruise at .92

18 Wheeler thankyou I did'nt know the 747 could cruise at M.92 also. I guess it probably is the fastest then ( I have to now admit defeat to my friend )

[18-Wheeler]

G-ALAN, this is my best effort in a 747 -




It was done on a systems test flight, so all approved & so on.
I know of crews that have cruised at M 0.90 in them for an hour or so though ...

[HotDog]

Our test flight schedule under HKG CAD rules was the same by the looks of it. I've done about six of them during my flying days.

VMO [at FL300] - record readings on both ASIs (337 - 345Kts.

High Mach Warning [to not below FL250.] Using MC EPR, accelerate to, but DO NOT EXCEED 0.92 MMR. Check and record both pilots Mach (0.895 - 0.920 MMR),IAS and altitude at the warning.

Sound familiar 18-Wheeler?

[747FOCAL]

No4,

Well your kinda correct. They did a split S and tore off 2 or 3 slats.

The pilots did lower the flaps just slightly and then pinned it with a clamp or vice grips. To do this they had to pull the breaker for the leading edges. Well, they forgot to tell the FE and when he returned from the bathroom, noticed the breaker out and pushed it back in. BAM, out came the leading edges.

What do you bet them 2 pilots never flew PAX again?

[CAT1]

The story of pulling CB's and not telling the F/E is not neccassarily true. To me, it sounds extremely unlikely. I've tried it in the sim and there is no performance advantage in deploying trailing edge flap at altitude in the 727: in fact, it slows down. The NTSB's case was based on the F/E saying he'd left his seat for a minute before the incident: he later said he had not in fact left the flight deck but had merely deposited some food trays at the rear of the flight deck. This was omitted from the NTSB's report. Also, the idea of pulling CB's without telling the F/E, who sits right next to them, is ridiculous.
It was also claimed the captain had erased the CVR: this was impossible, as the gear was so damaged during the extension at M1.1 that the ground/air switch could not have been functioning. The FDR cannot be erased without the aircraft being on the ground with all three engine driven generators offline and the parking brake set.
The actual cause was most likely an uncommanded deployment of No.7 leading edge device: there have been other instances of this occuring, including to a friend of mine (luckily at low speed). Easier to blame the crew than ground the type.

[747FOCAL]

CAT1,

If he flew for another 30 minutes afterwards the CVR would have recorded over the area in question. My information on the incident comes from the at the time Director of Engineering for the airline. I can look around for the FAA report on the incident.



ps. The 727 sim is not representative of actual aircraft performance. Ask anybody who builds and maintains them. Replicating drag in an electronic environment back when the 727 was built was almost impossible. You may be able to do stalls in the sim but try a heavy aft cg stall in an actual 727 without a pilot that has done it before and most likely you are dead.

[G-ALAN]

Nice pic Don't airliners have a Vno before you reach the max speed? Maybe it works different with the big boys. All I know is on the aircraft I fly if I go above VNE (161kias) for too long the wings drop off and if I go above VNO (118kias) for too long in turbulence the wings also fall off and I become a lawn dart

[CAT1]

The point I made as to the CVR was not what was or was not on it but the fact that the NTSB claimed Capt. Gibson erased it after landing. This was impossible: the gear collapsed when they tried to tow it. Gibson himself believes the problem was caused by the rudder, and the slat failed later. His petition to the NTSB (which was unsuccessful) can be found at
http://www.iprr.org/COMPS/pet727/PFR2.htm

I stand by my assertion that pulling CB's without telling the F/E goes against any principles of airmanship, and Gibson was, before the incident, a well-respected pilot.

As to how realistic the sim is: Deploying No7 leading edge slat with autopilot engaged at FL410 and then failing the autopilot caused it to roll inverted, and reach M1.2 vertically within a very short space of time: remarkably similar to the Gibson incident. Except the crew could not recover it.