T/O Engine Performance

[RealisticObserver]

What is the company policy on T/O and climb engine performance. To the more observant traveler, (and those upfront who hear the 757 engines) US uses max power (or what ever the load calc identifies) for T/O and initial climb and then throttles back to 75-80% power at what seems to be 3,500ft and at about the same time as the rear flaps are retracted.
I know that SWA does the complete opposite in terms of T/O with 85% power (whatever load calc identifies), and then throttles up to what seems to be 100% power upon retraction of the flaps. However, was just on a US 734 this past weekend out of CLT, and the pilot used max power and kept all the way on max until 10,000ft before throttling back. My memories of flying United are that of full power until 10,000ft before throttle back also.

What is the company policy for this, and why is it chosen as such. What does this do for engine wear and tear and longevity.

Also, on a side note, was also on a US East 319 (old colors) which still had the closet up front, and the galley across from the closet. Same with the 734. I thought all of that was removed. And oh, bulkhead seats in the 734 are the most claustophobic seats in the world......

 

[nethan]

I'd say when I'm up front on a jumpseat (which happens WAY too much on my commute) the majority of the takeoffs are flexed/derated on the Airbus and 757s. I don't know about the other fleet types though. On the Express side in the RJs pretty much everyone here flexes their takeoffs when ever they can. There are times (short runway/heavy, need anti ice on, thunderstorms, gusty winds etc) when we can't but other than that, everything is flexed.

Also, I doubt anybody is taking off with "max power". Maybe max take off thrust.

 

[autofixer]

Standard USAirways thrust is reduced or balanced thrust takeoffs. At 1000' above the ground the procedure is to reduce to climb thrust (1500' internationally) which can also be reduced on Boeing and E-190 aircraft. I don't believe US does this any differently than any other airline in the world.

 

[nycbusdriver]

You can't tell from a passenger seat what power setting is being used for takeoff. I don't care if you are a Super-Duper, Double-Secret, Presidential Platinum-Laced-with-Diamonds FF.

The power setting used for takeoff is dependent on a lot of factors. It is usually more than what is set at approximately 1000 feet above the ground, when you can indeed hear the power change....usually.

SWA climbing to 10,000 feet without changing power simply means that the climb power required in that case was the same as the required takeoff power setting, hence no change during the climbout. It's rare, but it happens when loads are light, weather is cool, runways are long, and engines are very powerful for the airframe.

 

[RealisticObserver]

I was waiting to hear your response, as I believe from your tag, you are indeed a pilot. My initial post was more of a question based on sound and feel of the airplane from a passenger perspective, and not an exact scientific comment. I have no idea about settings, and the difference between thrust and power, which is why i asked the question initially.

Therefore, going back to my original post, it sounds and feels like US throttles back shortly after takeoff, where as it sounds and feels like SWA throttles up at the same juncture where US throttles back, and where United keeps a flat setting until 10K, as did the US 734 this weekend. Please intrepret the word "throttle" as an encompass for power and thrust settings, whatever the case may be. And regardless of what the power/thrust settings are for T/O, US always seems to reduce after the initial climb.
And by the by, traveling mostly transcons on 321's, I would be willing to bet that those engines are pegged for T/O everytime. I have been on a PHL-SFO flight where PHL takeoffs were on 9L, and the pilot asked for a special takeoff on 9R because he said he needed the extra runway, and yes he announced as such to the cabin.

 

[A320 Driver]

I was waiting to hear your response, as I believe from your tag, you are indeed a pilot. My initial post was more of a question based on sound and feel of the airplane from a passenger perspective, and not an exact scientific comment. I have no idea about settings, and the difference between thrust and power, which is why i asked the question initially.

Therefore, going back to my original post, it sounds and feels like US throttles back shortly after takeoff, where as it sounds and feels like SWA throttles up at the same juncture where US throttles back, and where United keeps a flat setting until 10K, as did the US 734 this weekend. Please interpret the word "throttle" as an encompass for power and thrust settings, whatever the case may be. And regardless of what the power/thrust settings are for T/O, US always seems to reduce after the initial climb.
And by the by, traveling mostly transcons on 321's, I would be willing to bet that those engines are pegged for T/O every time. I have been on a PHL-SFO flight where PHL takeoffs were on 9L, and the pilot asked for a special takeoff on 9R because he said he needed the extra runway, and yes he announced as such to the cabin.

The A321 is a little interesting. There is a LOT more thrust available for takeoff then there is for climb. I saw an engineering document once that described this. The Thrust limit was boosted to meet contracted takeoff thrust, but the climb thrust limit was NOT boosted. That is probably why it seems to be such a huge difference between takeoff thrust and climb thrust. Completely normal for an A321. NYCbusdriver described the other conditions perfectly. A321s are flown heavy...lots of west coast flying. But that doesn't mean full power is always used, but I'm sure it sounds/feels that way in the back.


Driver B)

 

[strangiatotheme]

What is the company policy on T/O and climb engine performance. To the more observant traveler, (and those upfront who hear the 757 engines) US uses max power (or what ever the load calc identifies) for T/O and initial climb and then throttles back to 75-80% power at what seems to be 3,500ft and at about the same time as the rear flaps are retracted.
I know that SWA does the complete opposite in terms of T/O with 85% power (whatever load calc identifies), and then throttles up to what seems to be 100% power upon retraction of the flaps. However, was just on a US 734 this past weekend out of CLT, and the pilot used max power and kept all the way on max until 10,000ft before throttling back. My memories of flying United are that of full power until 10,000ft before throttle back also.

What is the company policy for this, and why is it chosen as such. What does this do for engine wear and tear and longevity.

Also, on a side note, was also on a US East 319 (old colors) which still had the closet up front, and the galley across from the closet. Same with the 734. I thought all of that was removed. And oh, bulkhead seats in the 734 are the most claustophobic seats in the world......

Takeoff and climb thrust settings are dependent on a number of variables, most of which a passenger would never know and nearly all of which are not specific to a certain airline. You can't generalize these types of things.

 

[mikey60]

Real

The 757 rarely uses full power for takeoff we normally use a "reduced thrust" power setting that is computed for us. Takeoff power can be reduced 25% using this system. It increases engine life. These engines are make by Rolls Royce ( on US airplanes) and produce 42,000 lb of thrust. At some airports like STT and LAS in the summer you do need max. power. I don't think many jet aircraft use t/o power to 10,000 ft. It would exceed engine limitations .

 

[LD3]

SWA climbing to 10,000 feet without changing power simply means that the climb power required in that case was the same as the required takeoff power setting, hence no change during the climbout. It's rare, but it happens when loads are light, weather is cool, runways are long, and engines are very powerful for the airframe.

Rookie question... aren't light loads and cool weather an engines best friend? Wouldn't you be able to reduce climb thrust thus reducing fuel burn?

 

[flyinawa]

Therefore, going back to my original post, it sounds and feels like US throttles back shortly after takeoff, where as it sounds and feels like SWA throttles up at the same juncture where US throttles back, and where United keeps a flat setting until 10K, as did the US 734 this weekend. Please interpret the word "throttle" as an encompass for power and thrust settings, whatever the case may be. And regardless of what the power/thrust settings are for T/O, US always seems to reduce after the initial climb.

Pretty much all data used by large jet aircraft is based on climbing to "Thrust Reduction Altitude" (normally 1000' above the ground) at a predetermined "take-off" power setting and then reducing to a "climb" setting. Also normally at 1000' above the ground is "Acceleration Altitude" which is when the pilots lower the nose of the aircraft slightly to help accelerate to "Climb Speed" which is normally the speed at which the aircraft would be at the best "lift to drag ratio". The 1000' number may be higher due to mountainous terrain in the vicinity of the airport (*think Reno, which is in a valley surrounded by mountains) or very congested areas in the departure path. The ideal take-off power is the lowest thrust setting which would allow the aircraft to safely continue to climb on one engine if the other failed beyond a predetermined speed (V1). In the Airbus, that reduced amount is the "Flex" (flight level change) power setting. While the pilots have the option of choosing a higher power if they feel it is necessary for reasons such as a wet or snowy runway or following a "Heavy" aircraft (capable of takeoff weights of more than 255,000 pounds whether or not they are operating at this weight during a particular phase of flight) which would generate more wake turbulence, doing so unnecessarily is a waste of fuel and unnecessarily decreases the time between maintenance intervals. At some point the aircraft performance may dictate using Max or "TOGA" (take-off, go-around) power. If this Max setting would NOT be enough to maintain required single-engine climb requirements, then the weight of the aircraft would have to be reduce, typically by reducing the number of passengers on-board and leaving with empty seats. Hot outside air temperatures and high altitude airports are also a major factor in determining power output of the engine and thus max take-off weight. Truth be told, in the event of an engine failure during a reduced power takeoff, the thrust on the "good" engine could always be manually set to "TOGA".

So, to answer your question...
I would be willing to bet if a UAL Airbus and a USAir Airbus both took off the same runway at the same weight, they would use roughly the same take-off thrust setting. I wouldn't think individual airlines would tinker with performance data too much because the power set for take-off is contingent on the "what-if" engine loss. If a particular airline used a lesser power setting and an engine actually DID fail, they would be liable if the outcome was catastrophic.

You're observation about SWA increasing thrust after take-off is very astute. Some of the 737's they fly are real powerhouses and while they take-off at a much reduced power for the reasons I mentioned above, they don't have a "reduced power climb", so the engines actually increase to a higher power setting at "thrust reduction altitude".

And by the by, traveling mostly transcons on 321's, I would be willing to bet that those engines are pegged for T/O everytime. I have been on a PHL-SFO flight where PHL takeoffs were on 9L, and the pilot asked for a special takeoff on 9R because he said he needed the extra runway, and yes he announced as such to the cabin.

At an airport with multiple runways, since departing aircraft require longer runways than landing aircraft, the runway(s) used for take-off are typically the longest. Sometimes, for ground traffic management, "long" is long enough for departing aircraft and airports like Philly will use the one that is that is most convenient. When performance dictates the use of a different runway then the airport is trying to use, pilots can request alternate runways. Unfortunately, sometimes it takes time to be worked into the flow of traffic. That time delay is the only reason I can think of as to why the pilots would announce their intentions to the passengers. I can't imagine most of you would care what runway was used for departure or why, as long as the aircraft arrives at the destination on time.

 

[DHG750R]

Rookie question... aren't light loads and cool weather an engines best friend? Wouldn't you be able to reduce climb thrust thus reducing fuel burn?

You are correct !

 

[RealisticObserver]

Thanks for you detailed explanation. I appreciate your time.