727 questions

gay_pilot18

gay_pilot18

New Member
Okay quick question for Doug and DE727UPS and all others who wanna chime in on this question. The B-727 was orginally built by Boeing as a STOL high lift airplane with it's large triple slotted fowler flaps and krueger leading edge slats. It was meant to fly outa smaller airfields with runways lenghts anywhere from 4-5,000ft.

So my question is everytime I see them take off (when we at Delta still had them) and I mean EVERYTIME they eat up most of the runway on take-off. The runways here at CVG are 10,000ft. I see fully loaded 767's going to europe use less runway then a 727. And before anyone says anything I know some flights that didn't go out heavy with fuel or passengers (CVG-SDF for example). But these flights still got airborne almost just before the numbers So again my question would be why?
 
Probably because of two things:

The engines have been hushkitted, probably degrating their abilities.

Secondly, the pilots probably aren't using "full" power (for lack of a better term) for noise abatement reasons. When I was practicing in the sim, we were instructed to use 1.96 EPR. I'm guessing that today's pilots are being instructed to use a lower EPR for noise.

These are two of the reasons I can come up with. They're probably wrong, but please don't flame me if I am.
 
Delta (and most other airlines) computes derated takeoff data to save wear and tear on the engines. Practical consequences of this is that most, if not all, takeoffs will be planned to use the least amount of thrust possible for that runway, temperature, pressure altitude and wind conditions. As a result of using the min thrust absolutely necessary, most of the runway will be taken up in the takeoff roll, while still leaving the minimum amount of runway necessary in case of a rejected takeoff. If a short runway takeoff is required, a higher thrust up to Normal or even Maximum thrust can be computed, resulting in a safe takeoff on the short (5000') runway example, but also resulting in more wear on the engines.
 
[ QUOTE ]
Delta (and most other airlines) computes derated takeoff data to save wear and tear on the engines. Practical consequences of this is that most, if not all, takeoffs will be planned to use the least amount of thrust possible for that runway, temperature, pressure altitude and wind conditions. As a result of using the min thrust absolutely necessary, most of the runway will be taken up in the takeoff roll, while still leaving the minimun amount of runway necessary in case of a rejected takeoff. If a short runway takeoff is required, a higher thrust up to Normal or even Maximum thrust can be computed, resulting in a safe takeoff on the short (5000') runway example, but also resulting in more wear on the engines.

[/ QUOTE ]

I was kinda right!! Yay!!!
 
Well not that I have any great amount of experience with the 727 but this would my answer(guess) in general - just because an airplane CAN do something doesn't necessarily mean it's a good idea to do that all of the time. In any airplane usually to do one thing well you have to sacrafice something else - you can put some more flaps down and get off of the runway in less amount of distance but your second segment(initial climb performance) can suffer and that becomes imortant if you lose an engine. So if I have the runway available I would rather have a longer takeoff roll and better initial climb performance.

Also - many airlines use 'reduced thrust takeoffs' to reduce wear on the engines. Instead of max take off N1 being maybe 92.0% they may reduce it on longer runways to say 88.5% - less thrust means longer take off rolls but less wear on the engine.

That would be the generic answer.

Jason
 
Reduced thrust takeoff data is also used when possible because most airlines have engine reliability programs that are predicated on this reduced thrust figure. Using reduced thrust extends an engines "life" before overhaul by as much as 15%. Multiply this by several hundreds (or thousands) of engines in an airline's inventory, and you're looking at operating savings easily topping several million even for a regional airline.

In the event of a failure of an engine during a reduced takeoff, max thrust is always available, and in fact some aircraft automatically increase the remaining good engines to max thrust in the event of loss of an engine (at least the CRJ does.. any others?).

Paul
 
I think the -100 was more of a STOL aircraft.

But all of the other answers are correct. Hushkitting, de-rated power takeoffs, rolling takeoffs, normal flap settings, etc add into the takeoff roll.
 
Well guys and gals thanks for all the excellent post I love hearing from each and everyone of you. Ever since I was a kid I have loved planes and I have always loved to watch planes take off high into the sky so I'm more a fan of STOL.

When I was still getting my private pilots license my instructor wouldn't allow me to touch the flap lever after we completed the run-up because I would always wants to put in 10 notches of flaps for a short field takeoff on the C-172. My instructor always preferred a normal no flap takeoff. He would always yell at me. "Sterling take or hand off the flap lever, Sterling don't even think about lowering the flaps".

In time maybe when I mature some and become less of a "hot dog" experience will teach me differert but for now I absolutely love short field takeoffs.

As for the 727 there prolly not taking off on full power but damn I'ma gate agent @ CVG and I'll be a F/A when Delta starts hiring again so I see everything and 757 takeoff mostly before mild field and there pilots prolly just like 727 pilots are not using full take off thrust and they often get up at or before mid-field.

The 727 has higher lift devices on it's wing then the 757 and one more engine so why is the 727 such a "pig". In addition to takeoff performance I have heard many pilot say that the 727 has very poor climb performance to "flight level". I love the takeoff performance of the 757 no commercial jet has it's climb performance it is just a beautiful plane.
 
V speeds for a 160,000 lb 727-200 at different take-off flap settings.

Flaps 5- V1/VR- 140 kts V2- 154 kts

Flaps 15- V1/VR-132 kts V2- 146 kts

Flaps 25- V1VR- 123 kts V2- 137 kts

Flaps 15 departures are the most common, and I've only done 1 flaps 25 departure and that was on a hot night in a heavy -200 out of Brownsville, Tx, on a short runway.
 
I am no expert on B727 but i have taken a flight engineering class while i was in college. Anyone feel free to correct me on my response. The B727 and B737-100-200 series engine have turbo jet engines as compared to a B767 or other newer version wide or narrow body jet, which have high bypassed TURBO FAN engines. Since a turbo jet engine does not have no added features such as fan, propeller, or free turbine- they are also known as straight jets. Therefore, a turbojet engine mainly relies on ram air especially during takeoffs. This is one of the primary reasons why you see B727 and other turbo jet engine clean up pretty much the entire length of the runway.
 
Actually, the reason has nothing to do with any of the above responses. The fewer the engines the better the all engine performance will be, as the performance minimum requirements are based on the engine inoperative scenario. As a result, a twin on one engine has to be able to perform as well as a tri on two engines or a quad on 3 engines. That, in turn, means that you have quite a bit more excess thrust with all engines operating in a twin.
 
Another thing to consider...

Was way back in the day when the 727 was designed to get in and out of short runways like LGA, HOU, and MDW...the competition was like 707's and DC-8's with early model turbojet engines. The 727 with "the wing that comes apart" was a great short field performer at the time. Nowadays, though, with the high-bypass turbofans and excellent thurst to weight ratios, I don't think of the 727 as a short runway plane. Pretty sure a 757 can go anywhere we can...
 
Re: Another thing to consider...

Eastern operated regular scheduled service from Miami - Key West with 727's in the 70's. That was back when the runway was only 3900'. They weren't very weight restricted either.

--03M
 
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