747400sp From United States of America, joined Aug 2003, 3183 posts, RR: 3 Posted (6 years 15 hours ago) and read 7890 times:
The 727 was a pretty fast plane compared to the DC-9/MD-80, 737 and A320. It had a cruising speed of mach 0.84, it faster the a 707 and MD-11 mach 0.83 and the same speed as a 747-100/200 and L-1011. But lately there speed been reduce to mach 0.78 around the same as a MD-80, 737 NG and A320. Why have they reduce the 727 speed so much?
When the 727 starting flying at 0.84M, fuel was $0.10 per gallon.
Slowing down to 0.80M or so saves a lot of kerosene.
Another factor is that it was routine in the mid '60s to fly at Mmo. If you overspeed slightly and set of the overspeed warning horn, it was not big deal.
Today, the FBW systems start pulling back the throttle or pitching up if you get within 0.005M of Mmo.
And if you do exceed Mmo and the FDR or datalink tattles on you, the Flight Ops department will launch an investigation of your piloting skills.
So much for the days of leather jacket/white scarf aviators.
Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
Access-Air From United States of America, joined Sep 2000, 1938 posts, RR: 22 Reply 5, posted (6 years 11 hours ago) and read 7744 times:
Id say that more than likely that it was just to save fuel.....
If you look at old airline schedules and you compare the flight times say back in the 70s with what they are today, some of the flighst can be up to 20 mins faster than today...But then it prolly also accounts for the extra air traffic congestion and that I beleive at one point the FAA was fining airlines for late flights so to counteract the late flights they would pad their schedules so they had some wiggle room in case of ATC delays or whatever....
CosmicCruiser From United States of America, joined Feb 2005, 2045 posts, RR: 18 Reply 7, posted (5 years 12 months 4 days 18 hours ago) and read 7553 times:
Quoting Liedetectors (Reply 6): a hush kit can kill the performance of an engine.
I don't think that has anything to do with cruise mach. We had hush kits on ours at FEDEX and we flew the same cruise always. The -200 could go very, very fast! LOL More than likely it's fuel savings.
Access-Air From United States of America, joined Sep 2000, 1938 posts, RR: 22 Reply 8, posted (5 years 12 months 4 days 16 hours ago) and read 7517 times:
I wonder if it also has to do with the fact the 727 has a relatively short wing span for its size...It also seems to be pretty thin as well...
Technically speaking the 727-200 (153 feet) is one foot longer than the longest 707-300 series(152 feet) ....however I believe the wingspan is only like 108 feet long on both the 727-100 and 200....vs like 146 feet on a very wide chorde 707 wing.
I have personally watched a United 727-100 rocket off of a 4700 foot runway in Moline headed for Denver and it only used maybe half of it....It was awesome...I audio tape recorded it too, however I wish I had video camera back then....grrrrrrrrrrr!!!!
CosmicCruiser From United States of America, joined Feb 2005, 2045 posts, RR: 18 Reply 10, posted (5 years 12 months 4 days 15 hours ago) and read 7485 times:
Economy cruise calculated by the FMS based on input CI, Cost Index. We use CI 200 which usually results in about .832-.835M. I can edit the speed to whatever( not to exceed high speed buffet) but from .850 or greater you can definitely see an increase in fuel burn. The 727s have a given "econ" cruise still about .820-.830 (best I remember) that they use but our policy is if you're running late and may miss the sort ..go fast.
Greasespot From Canada, joined Apr 2004, 3015 posts, RR: 26 Reply 11, posted (5 years 12 months 4 days 6 hours ago) and read 7361 times:
Quoting Liedetectors (Reply 6): Many 727s have hushkits on them. a hush kit can kill the performance of an engine.
Hush kits do not affect the performance of the engines.
Most B727's are freighters and have a cargo door. Because of the door they are speed restricted. I cannot remember what the Not to exceed speed is... Going from memory it is 350knots ( i think)...
Plus as said earlier it is cheaper to fly slower than fast.
GS
Sometimes all you can do is look them in the eye and ask " how much did your mom drink when she was pregnant with you?"
CosmicCruiser From United States of America, joined Feb 2005, 2045 posts, RR: 18 Reply 12, posted (5 years 12 months 4 days 4 hours ago) and read 7321 times:
Quoting Greasespot (Reply 11): Because of the door they are speed restricted.
It's been about 10yrs. since I last flew a 727 but I don't think there was any speed restriction because of the cargo door. Just checked the 727 manual and it says 350kts @ S.L. 370kts/.880m @ 25,000'. The only speed restriction associated with the cargo door is 250 kts. with a main cargo unlocked indication.
Greasespot From Canada, joined Apr 2004, 3015 posts, RR: 26 Reply 14, posted (5 years 12 months 3 days 12 hours ago) and read 7142 times:
Quoting CosmicCruiser (Reply 12): It's been about 10yrs. since I last flew a 727 but I don't think there was any speed restriction because of the cargo door.
Maybe it is the ones modified with the AEI doors. I know our -200s have mode B (if that is the faster mode) on the ASI locked out.
GS
Sometimes all you can do is look them in the eye and ask " how much did your mom drink when she was pregnant with you?"
Corey07850 From United States of America, joined Feb 2004, 2500 posts, RR: 5 Reply 15, posted (5 years 12 months 3 days 10 hours ago) and read 7113 times:
IAHFLYR From United States of America, joined Jun 2005, 4136 posts, RR: 28 Reply 16, posted (5 years 12 months 1 day 13 hours ago) and read 6954 times:
CosmicCruiser From United States of America, joined Feb 2005, 2045 posts, RR: 18 Reply 17, posted (5 years 12 months 1 day 9 hours ago) and read 6877 times:
Quoting IAHFLYR (Reply 16): WOW an FMS in a B727......lovely, any glass panels?
I was responding to an earlier post that said the MD-11 did .83 and I posted that .830 is just econ cruise and we can go faster if we wish. The 727 is the same in that the co. flight plans them at about .82-.83 but they can and do go faster especially if they're running late.
If you want to cruise at .76/.78/.84/.90 go for it.
But if your following other traffic thats at .78 then ATC will have issues with you and tell you to slow up/speed up or vector you out of sequence. That would burn more fuel than going at .78 - along with the crowd.
.78 probably gives the best distance traveled against time with the best fuel burn.(NextGen engines aside.) Its like traveling along the highway at 70MPH compared to 80MPH. You'll get there faster but you'll burn more fuel.
KD
Liedetectors From United States of America, joined Jul 2005, 356 posts, RR: 0 Reply 20, posted (5 years 12 months 8 hours ago) and read 6706 times:
Quoting TheSunseeker (Reply 19):
I thought Trump, for example, has the 727 because its FAST!
his 727 will be faster then most because he doesnt carry the passenger load that a conventional 727 would. he probably carries 10 pax on that thing at any time.
DC3CV3407AC727 From United States of America, joined Dec 2003, 314 posts, RR: 3 Reply 21, posted (5 years 11 months 4 weeks 21 hours ago) and read 6594 times:
its all about the fuel,we cruise at Long Range Cruise settings (LRC),that put us at .78-.80 mach for cruise,but we are fully capable of any speed up to our limiting mach of .88 if the situation,or mission demands it.
the rumble of round engines is like music to me,likewise the thunder of thr JT8D
Miamiair From , joined Dec 1969, posts, RR: Reply 22, posted (5 years 11 months 4 weeks 19 hours ago) and read 6582 times:
As airplanes age, they accumulate weight from mods, repairs, dirt, etc. which can contribute to slower speeds. External repairs, peeling paint, surface rougness will all increase drag.
EssentialPowr From United States of America, joined Sep 2000, 1820 posts, RR: 2 Reply 23, posted (5 years 11 months 3 weeks 4 days 12 hours ago) and read 6430 times:
Why are the airlines losing money??? A 727 can't increase fares, but it does burn a lot of gas to go fast...
Oryx From Germany, joined Nov 2005, 126 posts, RR: 0 Reply 24, posted (5 years 11 months 3 weeks 3 days 19 hours ago) and read 6374 times:
Quoting Greasespot (Reply 11): Hush kits do not affect the performance of the engines.
Some do.
It's allways a challenge to get the noise down without increasing fuel consumtion or decreasing performance. Even more so when modifying an already existing design.
25 SlamClick: It should be mentioned also that it is rather difficult to get around another plane flying the same route, even if you are M.06 or M.08 faster. That i
26 Starlionblue: And we all know those Citations are sometimes struck by birds from behind.[Edited 2006-06-06 19:38:36]
27 Miamiair: Are you implying that the Citation has a calendar instead of an air speed indicator?
28 SlamClick: Oh no! It has an airspeed indicator. It is made by Smiths and reads in furlongs-per-fortnight.
29 Starlionblue: Maybe it would help if it could take off from a conveyor belt...
30 hmmmm...: Keep in mind that the 727 was just a faster plane than today's planes, so it has to slow down to stay in the line. A plane's cruising speed is determi
31 HaveBlue: Damn you hmmmmm, you resurrected a 6 year old thread! I saw a reply by SlamClick, one of the most esteemed members and one of my favorites, and got al
32 Max Q: You don't always save fuel by slowing down, in the B727 you could save fuel by flying .83 to .84 mach into a headwind. Spending less time in the air m
34 clydenairways: Its all about money. Most airlines these days have fairly strict fuel economy SOP's, so the pilots are told what cruise speed to fly at. This speed wi
35 bhill: Curious, if properly maintained per manufacturer specs and FAA regulations should age ever be a contributing factor with regards to MM numbers?
36 Max Q: Don't know where you get that information. At my Airline the cruise speed is left up to the Pilots based on the situation.
37 clydenairways: Most Airlines i know in Europe have SOP's for Fuel Economy these days, and line pilots are expected to follow them, unless there is a valid reason no
38 Max Q: Makes no sense to me, taking the discretion away from the Pilots to operate as needed is shooting yourself in the foot.
39 vikkyvik: Same here. He does pop up from time to time. Have to be paying attention to catch him, though. Isn't what he's describing basically Cost Index? You e
40 Viscount724: Actually 3 inches longer. 727-200 153 ft. 2 in. 707-320 152 ft. 11 in. However the 707-320 fuselage is 9 ft. longer than the 727-200 fuselage. The 72
42 Max Q: Not where I work, the Company tells us to use whatever cost index is necessary to provide the best result. If we are running late we will go as fast
43 B777LRF: To summarise: The 727 is still as fast as it ever was. The only thing that's been lost is the airlines willingness to spend money flying fast, unless
44 Fabo: It is the best result part that varies. IIRC I read in some (passenger) airlines manual that going fast to shave off few minutes is advisable, but on
45 glen: It is not a good thing for fuel economy to go faster in case of headwinds, but it is good for the overall-costs of a flight. CI is the relation betwe
46 Max Q: The FMC will increase Econ cruise mach with an increase in headwind. I disagree, while increasing speed into a headwind may seem counterintuitive my
47 clydenairways: I never said that. I think you are misunderstanding me. If that is your company SOP then fine, but if it's not and you still decide to do it anyway t
48 Starlionblue: That's what glen said in the second half of the sentence you are quoting.
49 glen: Even if you spend less time in the headwind it is always the same ESAD (equivalent still air distance) you have to travel, independent of your speed
50 tdscanuck: It shouldn't make a difference. As airplanes age they get heavier and the engines get thirstier so it might take you a little more fuel to hit the sa
51 clydenairways: Your right, most don't. But there are a few things a company can do to change this, if their type of operation allows it. Negotiate a change in some
54 brons2: Is the 727 subject to mach tuck at all?
55 tb727: Not to my knowledge. I don't think the aerodynamics would really allow it. The only aircraft I have ever flown were mach tuck was a concern was the L
56 Max Q: Boeing tested the B727 to .96 Mach with no adverse handling effects. And 'Hoot' Gibson of TWA took it through Mach one, it held together just fine, ev
57 Fabo: I disagree, ESAD will not be the same. Compare the examples: You are flying a 200nm ground distance track, directly against a steady, 100kt headwind.
58 glen: You are right, a while after I wrote this it also came to my mind, that ESAD is depending on actual speed. But I'm still sure, you won't save fuel by
59 Fabo: Yes, but it is also true jet engines work more efficiently at higher RPM, so they might infact generate 2.25 thrust with 2 times as much fuel, of cou
60 Max Q: Well, I can tell you that in over 25 years flying jets that flying faster (within reason) into a headwind will save you fuel. Theories are just that
61 tb727: Ditto! I push them up into a headwind and pull them back(reluctantly ) with a tailwind.
62 glen: Well, I have also 20 years on jets, but never on a such a lady like a 727 or similar - all aircraft I flew were always FMS-equipped. I was never payi
63 aircellist: Fairly logical, when one thinks of it... Learned something. Thanks!
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