Reduced power Take Offs?

4 percent??

...a way to reduce my chances of having an engine failure on takeoff to less than 4%. I liked those odds...

Am I missing something? Why is it good to have an even chance of an engine failure on every 25th takeoff? Now I'm nervous, cause I am way, way overdue.

Did a decimal point, and maybe some zeros, get omitted?

Just wonderin'

Fuzzy Math

OLDSAM said:

...a way to reduce my chances of having an engine failure on takeoff to less than 4%. I liked those odds...

Am I missing something? Why is it good to have an even chance of an engine failure on every 25th takeoff? Now I'm nervous, cause I am way, way overdue.

Did a decimal point, and maybe some zeros, get omitted?

Just wonderin'

Click to expand...

What was said is the 96% of engine failures on TO occurred at full power. So now we need to estimate what the percent chance of engine failure is on TO. NTSB-AAS-72-10 shows that for single engine a/c the engine failure rate overall was 4.6 failures per 100,000 flight hours. It also said engine issues were responsible for 44% of those failures (pilot error, fuel exhaustion, etc. made up the rest). Engine failures during TO Are estimated to be to be 30% according to a Boeing study. This results in 4.6*.44*.30=.61 engine failures/100,000 hours.

If you assume one TO per 2 flight hours this is an engine failure rate at takeoff of .0012144%. So if 96% of engine failures at TO occur at full power, then the failure rate during full throttle TO is .0011658%. So reduced power TO compared to full throttle (if the 96% to 4% applies), reduces the chance of engine failure by .0000486%.

Slow day at work...lol

Thoroughly enjoying this guys! Starting my second bag of popcorn right now. BTW, what kind of primer is the best in everyones opinion.......kidding, kidding....

Flying again! said:

What was said is the 96% of engine failures on TO occurred at full power.

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It is unwise to take off in our type of aircraft with anything less than full power...period. In a non-turbocharged single, lessening the time it takes to get to a safe altitude is the main concern. For a Turbo-charged engine without an automatic waste gate, full power would be whatever the limitations are.

The 96% thing is a total non-issue because almost all takeoffs in our little planes are accomplished at full throttle...most likely over 99%.

As a fixed pitch flyer, I'm at less than max power at every takeoff, correct? Also, formation takeoffs are at reduced,power to give wing power margin. We do that all the time.

fl-mike said:

As a fixed pitch flyer, I'm at less than max power at every takeoff, correct? Also, formation takeoffs are at reduced,power to give wing power margin. We do that all the time.

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Should have said "Max AVAILABLE power.
Yes, there are exceptions such as formation takeoffs and high altitude training.

Thank you for catching that.

Interesting thread !

I have never seen so many people ignoring factory advice.
In fact using full power for take off is not only suggested by the aircraft engine manufacturer but for once even the same advice is suggested by
APS's John Deakin.
These 2 entities are often at odds as to how to operate an aircraft engine.

It is unwise to take off in our type of aircraft with anything less than full power...period. In a non-turbocharged single, lessening the time it takes to get to a safe altitude is the main concern. For a Turbo-charged engine without an automatic waste gate, full power would be whatever the limitations are.

Click to expand...

It is just this simple

2 exceptions for me, noise abatement and formation take off.

engineerorange said:

That's usually because you are at max rpm (max piston speed/acc.) and when you let off the go pedal there is no boom to help turn the piston around and the rod and wrist pin have to do it all. You also get some shock cooling of the valves and every now and again a head pops off. Not to mention torsional reversals in the crank. Sometimes it gets ugly.

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I believe that when I was 16, but now . . . it is just hand waving, and irrelevant to a reciprocating engine. Every other stroke is intake, no pressure there. Those valves get shocked each revolution with hot exhaust gas and cool intake gasses, again - no issue. All systems/components are designed for much greater forces, temperatures than a "throttle back".

One main reason I am building an RV and not buying a Corvette, is I can legally use the RV to it's design capabilities. And I will. What thrill is a 200 mph Vette, tooling along at 55 mph. That alone would kill me.

When I drive my old E28 M5, yes, I absolutely push the pedal all the way down . . . a lot! Can't keep it there, it just goes too fast. It is made for it. I love it, it's why I have it. It has 155k miles too, no overhaul yet.

Part throttle or reduced power take offs are possible, and might extend the life of the engine (that is an whole other thread to rehash) so why not? Do it if you are safe, and if you want to. Personally, I have not decided on what each TO will be but, I will likely throttle back at 400 ft unless on a cross country mission that will need the speed.

Reduced power

I didn't build a hot rod ,big horse power , constant speed prop RV to do reduced power Anything !

You also get some shock cooling of the valves

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Not if you don't overheat them in the first place by lugging the engine with partial throttle, robbing it of the extra fuel needed for cooling as well as hot gas blowby heating the oil.

As I often point out, it is experimental aviation and you get to fly your engine any way you want

Here's my two cents as driver of airliners:

Reduced thrust take offs on airliners are good for safety, economy and noise abatement. There is a lower likelihood of gas turbine engine failure at reduced takeoff thereby improving safety. The aircraft will meet or exceed all required climb parameters even operating the remaining engine at reduced thrust. Additionally, the pilot has the option of increasing thrust on the remaining engine(s) to attain a greater safety margin in the climb. The economic and noise issues are obvious and have been extensively discussed here.

On normally aspirated single engine piston aircraft it is vital to have the best climb profile possible to reach an altitude from which an emergency landing in case of an engine failure can be safely made. By conducting a reduced power takeoff, you would be jeopardising safety. There are no proven benefits to enhancing engine life - you just may save some gas. That being said, I fly from noise critical airfields here in Germany and reduce rpm as soon as practicable whilst mantaining full throttle to lower the noise level

Maxrate said:

Thoroughly enjoying this guys! Starting my second bag of popcorn right now.

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Mounz said:

Here's my two cents as driver of airliners:

Reduced thrust take offs on airliners are good for safety, economy and noise abatement. There is a lower likelihood of gas turbine engine failure at reduced takeoff thereby improving safety. The aircraft will meet or exceed all required climb parameters even operating the remaining engine at reduced thrust. Additionally, the pilot has the option of increasing thrust on the remaining engine(s) to attain a greater safety margin in the climb. The economic and noise issues are obvious and have been extensively discussed here.

On normally aspirated single engine piston aircraft it is vital to have the best climb profile possible to reach an altitude from which an emergency landing in case of an engine failure can be safely made. By conducting a reduced power takeoff, you would be jeopardising safety. There are no proven benefits to enhancing engine life - you just may save some gas. That being said, I fly from noise critical airfields here in Germany and reduce rpm as soon as practicable whilst mantaining full throttle to lower the noise level

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You can't reduce the thrust on take off for an airliner to a point that you can can't make engine out climb performance criteria.

Airlines reduce the power for one reason, MONEY. The reduced temps prolong engine life, and when the first power reduction is made after takeoff you get a much smaller drop in temp then if you had been full power. i.e. it's a smaller "shock" to the engine.

Reduced thrust take offs actually burn more fuel. That's it, it's all about MONEY.


Get to altitude, get the power to cruise.

Willing to be educated, but...

So, I threw the first rock down this unstable slope, and I've appreciated all the posts that have avalanched as a result. I'm in the odd position of having zero significant piston time but 16,000+ hours total time. So I'm really asking to learn, not to promote a pet idea. My recent experience with airline take off procedures clearly may not translate to safe and practical piston ops - that's why I asked in the first place. I also asked about reduced power take offs in RV's, not Cessna 150's.
The take off and climb performance of RV's is so much better than nearly any other GA or Experimental aircraft (it seems) that routinely using every possible rev on all take offs seemed unnecessary. I get the impression that take offs done by (for example) setting Climb RPM from brake release and maintaining that power setting throughout the climb would still allow us to out climb nearly anything else as well as theoretically being easier on the motor.

That being said, I want to check back with the pros here on some of the comments made:

"...reduced power take offs burn more fuel..." Really? 'Splain that to me.

"...reduced power is harder on the engine than full power..." So, if reduced power take offs are hard, is idle murder? As I've said before, I'm willing and able to learn, but this doesn't pass the reasonableness check yet.

"...the airlines only do it for money..."

I won't address the first two comments due to my lack of knowledge of the subject. As for "...only for the money...", that's a really good reason in my books! I get profit sharing in my house: every dollar I don't have to spend becomes house profit and I get to share in it!

Thanks for all the chatter on this, guys, I appreciate it.

As high as I can, as quick as I can

and I start my crosswind as soon as it is practical (safe, noise abatement, obstacle clearance, etc.)---- my -6A gets me to pattern altitude by the end of the crosswind. From there, the "impossible turn" is not so impossible.

R.

"...reduced power is harder on the engine than full power..." So, if reduced power take offs are hard, is idle murder? As I've said before, I'm willing and able to learn, but this doesn't pass the reasonableness check yet.

Click to expand...

The engine is cooled via 2 mechanisms:

1. Airflow - in turn based on IAS and OAT
2. Running engine stupidly rich, so the unburnt excess fuel absorbs energy / heat (on the Harrier we used mineral water, which although expensive, I am sure was cheaper than Avgas!)

You can see the "excess rich" aspect if you try to run LOP as you climb at constant MAP - you need little mixture change until the throttle gets near full ('WOT'), then suddenly the fuel flow goes up.

I suspect the argument goes that on takeoff you have less cooling airflow, and if you now reduce power you eliminate the "extra rich" as well. A valid argument if your engine gets hot on takeoff, but with low OAT, a well cooled RV engine, and if the CHTs stay low, I doubt significant.

The get as high/soon as possible, maybe with a turn, has some validity - but taken to an extreme, you would always then remain in gliding range of an airfield, and join an airfield via the overhead, and do circuits always in gliding range. But most people die not through engine failure, but other (usually human) factors.

All risk management, as above, there are some valid reasons for reduced power takeoffs, but the "SOP" should likely be full power without good cause to reduce. Unlike us airliner types, where the MEL item requiring full power is good for a 30deg nose up rotate

claycookiemonster said:

So, I threw the first rock down this unstable slope, and I've appreciated all the posts that have avalanched as a result. I'm in the odd position of having zero significant piston time but 16,000+ hours total time. So I'm really asking to learn, not to promote a pet idea. My recent experience with airline take off procedures clearly may not translate to safe and practical piston ops - that's why I asked in the first place. I also asked about reduced power take offs in RV's, not Cessna 150's.
The take off and climb performance of RV's is so much better than nearly any other GA or Experimental aircraft (it seems) that routinely using every possible rev on all take offs seemed unnecessary. I get the impression that take offs done by (for example) setting Climb RPM from brake release and maintaining that power setting throughout the climb would still allow us to out climb nearly anything else as well as theoretically being easier on the motor.

That being said, I want to check back with the pros here on some of the comments made:

"...reduced power take offs burn more fuel..." Really? 'Splain that to me.



"...reduced power is harder on the engine than full power..." So, if reduced power take offs are hard, is idle murder? As I've said before, I'm willing and able to learn, but this doesn't pass the reasonableness check yet.

"...the airlines only do it for money..."

I won't address the first two comments due to my lack of knowledge of the subject. As for "...only for the money...", that's a really good reason in my books! I get profit sharing in my house: every dollar I don't have to spend becomes house profit and I get to share in it!

Thanks for all the chatter on this, guys, I appreciate it.

Click to expand...

On the first point... A jet engine is most efficient for fuel burn at full power. This however reduces the total life of the engine. The bean counters have figured out that the longer take off run, longer climb, and increased fuel burn to cruise is less costly than the early replacement cost of one engine. A CFM56 is $10m. Having spent a lot of my life executing bingo profiles and extracting the max range out of a pound of jet fuel... It sounds counter intuitive (and its REALLY uncomfortable going to full power in a fuel emergency!) I can tell you the math works. We could save tons of fuel in the airlines doing max power takeoffs, max power C/Lmax climbs to altitude.... However you would cut the life of the engine by orders of magnitude over what we currently get. Thus the benefit is in the higher fuel burn (over time) reduced power (lower turbine temp) takeoff and climb.

A reduced power takeoff in a piston engine, depending on how you do it may or may not lead to increased wear. 25" at 2700rpm vice 30" at 2700.... Less wear, less heat, but increased fuel burn to climb, overall higher total power setting for the average of that flight.

25" at 2500 rpm however and now you're slowing the engine down, and increasing the length of each combustion event. There's a graph somewhere I can't find that shows this leads to higher internal combustion pressures and higher heat, and higher CHTs as you're prolonging the climb to cruise airflow and reduced power setting.

I used to fly a Bonanza, 10-20 times a week over the same 50 mile leg, with a climb from 4k-9k. I did many different iterations of power settings, and can tell you unequivically the lowest fuel burn and lowest temps came from a full power climb, to a WOT, 2300 rpm, 50 degree LOP cruise (adjusted for TIT limits for a given day) to a cruise descent with cruise power set. There was no other profile I could fly to beat that without slowing to cruise at L/Dmax, but that would've cut speed by 1/3. Since it was a 135 operation we had to replace an engine at TBO and when it was pulled it was clean as a whistle inside, and was still running strong as new. (My advocacy for LOP operations in that last part.)

For great information on piston engine management Mike Busch is the man, his articles will explain a lot.

http://www.avweb.com/news/savvyaviator/

https://www.savvymx.com/index.php/resources/articles

claycookiemonster said:

So, I threw the first rock down this unstable slope, and I've appreciated all the posts that have avalanched as a result. I'm in the odd position of having zero significant piston time but 16,000+ hours total time. So I'm really asking to learn, not to promote a pet idea. My recent experience with airline take off procedures clearly may not translate to safe and practical piston ops - that's why I asked in the first place. I also asked about reduced power take offs in RV's, not Cessna 150's.
The take off and climb performance of RV's is so much better than nearly any other GA or Experimental aircraft (it seems) that routinely using every possible rev on all take offs seemed unnecessary. I get the impression that take offs done by (for example) setting Climb RPM from brake release and maintaining that power setting throughout the climb would still allow us to out climb nearly anything else as well as theoretically being easier on the motor.

That being said, I want to check back with the pros here on some of the comments made:

"...reduced power take offs burn more fuel..." Really? 'Splain that to me.

"...reduced power is harder on the engine than full power..." So, if reduced power take offs are hard, is idle murder? As I've said before, I'm willing and able to learn, but this doesn't pass the reasonableness check yet.

"...the airlines only do it for money..."

I won't address the first two comments due to my lack of knowledge of the subject. As for "...only for the money...", that's a really good reason in my books! I get profit sharing in my house: every dollar I don't have to spend becomes house profit and I get to share in it!

Thanks for all the chatter on this, guys, I appreciate it.

Click to expand...

Since you are committed to sticking with this question of reduced power takeoffs - what problem are you attempting to solve? For discussion, is it longer life to overhaul?, Lower operating cost per hour? Are you willing to compromise? Cruise speed, ?

Before delving in to answers, first lets understand the questions, that will establish the drivers and lead to discussion of solutions and tradeoffs.

Clay (and popcorn enthusiasts ),

I picked up on your original thought…that when flying rocket ships like RVs, why not used reduced power TOs to save $ and engine life…we do have a lot of margin in RVs, and it works at work, right?

I tossed out in my first post in this thread, a query to see if anyone has hard data on reduced power TOs being less wear on a recip. I don't think it is, but would be interested in engine mfgr findings…if there are any.

My gut says that its so critical to jet engines, because the heat and rotational forces are so high (as you know). 5,000 RPM for low speed compressors and turbines, 15,000 RPM for hi speed comp/turb (the limits are in that range). All that speed and heat trying to pull the blades out of the "sockets", etc. With the hours of service and history, they know that heat is the engine killer. Keep the heat down until the bypass air is flowing, and you save engine life…and loads of engine lease dollars. I recently saw a note that indicated that "the economic benefits of reduced power takeoff and initial climb diminish or vanish at 105 seconds after power-up". So the leasing companies have it figured out to the gnats ars, based on maintenance history. At that point we actually power back up for the rest of (the majority of) the climb. I've joked with FOs, "now that we're safely away from the ground, let's go to full power"…I'm sure many have. But there is is plenty of power to spare, as you know. However, I don't think reduced power takeoffs burn more fuel, as long as the operator doesn't waste time climbing to cruise (I think that's what Sig was referring to)

Bring it back to recips and RVs: The rotational forces are not as extreme, and the temps may not be as extreme (I'm not sure about temps though…it may be close.) It could be as simple as thinking it in terms of relative reduction of RPM: by that I mean that reducing a turbine 10-15 percent off of 5000/15000 RPM has a real impact, where reducing a recip an equal 10-15 percent of of 2500-2700 RPM may have a much smaller impact on heat generation. Also, the comments about reduced power takeoffs/climbs hurting recips are probably related to the carb or FI enrichment system. It may have been explained earlier, but at full power, a carb or FI system will meter extra fuel for cooling. Just off full power, that system does not operate. Interestingly the enrichment system is also known as the economizer system…which is not a good description of its impact on FF!

I'd still be interested in engine guru analysis or data on the impact to recip engine wear. My pref is to do full power takeoffs, and if noise abatement is a factor, I'll roll it back to 2500 RPM in the climb. However, I don't touch nuttin' till 1000' or so (for field return), as I've also heard what others have said: failures may be more prone to occur when the first change is made. I think that relates to an underlying problem lurking at a steady state, then popping its head up when the steady state is changed. Kinda like the zero oil pressure procedure in a single engine jet (TA-4 was my experience). Set XX%, and don't touch nuttin' till ya got the field made.

Again, just one technique (wrt RPTOs).

Cheers,
Bob

rvmills said:

. However, I don't think reduced power takeoffs burn more fuel, as long as the operator doesn't waste time climbing to cruise (I think that's what Sig was referring to)

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From an all other things being equal stand point (gross weight, atmospherics, AOA), a climb at full power vice 95% will burn less fuel. It sounds counter intuitive but for jet aircraft it's true. It's also why climb N1 will increase to 100% in the climb. The fuel/air ratio stays the same and with the decreasing air available fuel is reduced as well, thus lower exhaust gas temps flowing over the turbine, the driving force in engine life. It is also accurate to say that rotational speed limits could be exceeded under certain atmospheric conditions. Think Bingo profiles there Nasty, ever fly one at anything less than mil power in the climb? .

It is weird when you Go from takeoff to climb segments, and the auto throttles actually power up.

For the OP... if you have an engine analyzer go out one day and do a couple of climbs to say 8k' under varying power settings. Download the data (or take really accurate notes), then go home and compare them using the free analyzer at savvymx.

I may do it for fun, I don't think a couple of pounds of difference in fuel burn between each test will vary the test all that much.

Pat (Sig),

We're on the same page. If you extrapolate the reduced power TO to mean reduced power climb all the way to cruise, then yes, that will be less efficient, especially in a jet (concur on bingo pro's). I wasn't extrapolating that, probably because we do power up at work, and because I climb at full power in my RV. I was just saying that a reduced power takeoff by itself does not burn more gas than a full power takeoff…I think that is what the OP was questioning the validity of. The OP asked about reduced power TOs, so that's what I was focusing on. (Man, do I need to spell out everything LT? [joking ])

Reduced power climbs don't appeal to me either. Get up into the cooler air, get the engine dialed back for cruise, get the XM radio goin', and enjoy the view as you get downrange to wherever Vlad's party is. I'll bet most RVers, although blessed with mucho excess HP, will feign giving that excess up…once they've tasted it!

Should we start the debate over "climb flat, fly fast into a headwind; climb steep, throttle back" with a tailwind?

Cheers,
Bob

After some 70 responses this thread has about run its course.

Does it matter with these little engines?

Probably not....a Lycoming will run a long time at WOT with proper cooling and A/F mixture. It will also run a long time at reduced power, so it really does not matter.

Push the throttle up and enjoy it.

What about the dangers of reduced power landings?

David-aviator said:

After some 70 responses this thread has about run its course.

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Not quite - not even close.

We have yet to discuss the merits of reduced power landings. The Lycoming operator's manual is silent on this, however, I find that at less than full power I approach the ground more quickly. While making it easier to finish the flight, I don't believe it is as safe since going around should something foul the runway.

Reduced power landings are probably harder on the engine as well.

I'd also guess that they incur more costs, since a reduced power landing ends up on the runway and taxiway sooner, which means that the fuel pumps are that much closer. Using a full power landing tends to prevent this from happening.

Finally, I built an RV because I wanted to go faster than the average Cessna or Piper. Reduced power landings would seem to be counter productive here as well.

Thanks ChiefPilot

I was hoping we could get to the bottom of all this and include reduced power landings as well.

Technically the landing is only the portion were the aircraft touches the ground
preceded by the landing approach and followed by the landing roll.

I do use considerable power for landing on occasion and if the RV won't land I just call it a flyby. This approach results in increased costs but I make up for it by using full power on take off, thereby saving money on a premature engine overhaul... OK signing off now.

And what about reduced power taxi?

I know it probably uses more fuel, but it makes up by making the brake pads last longer.

ChiefPilot said:

Not quite - not even close.

We have yet to discuss the merits of reduced power landings. The Lycoming operator's manual is silent on this, however, I find that at less than full power I approach the ground more quickly. While making it easier to finish the flight, I don't believe it is as safe since going around should something foul the runway.

Reduced power landings are probably harder on the engine as well.

I'd also guess that they incur more costs, since a reduced power landing ends up on the runway and taxiway sooner, which means that the fuel pumps are that much closer. Using a full power landing tends to prevent this from happening.

Finally, I built an RV because I wanted to go faster than the average Cessna or Piper. Reduced power landings would seem to be counter productive here as well.

Click to expand...

Trying to follow your thinking here. Approach and landing is a function of controlling glide angle, airspeed, and factoring in stopping distance, runway length and wind conditions. Power and pitch are used to get the job done.

I suppose "reduced power" on landing could mean throttle closed on down wind leg and go find the runway dead stick - good stuff to practice but not practical at most airports with other traffic.

Reduced power (idle) is mandatory with a fixed pitch prop or you won't be landed and stopped in a reasonable distance. If your prop is CS, some power is needed to keep it from a flat pitch but not near full power. A full power approach and landing with the 8 is impossible, I'd be flying until fuel exhaustion at 160+ knots. The airplane will not go down an slow down at anything less than idle power.

The landing is critical. The subject of the thread is irrelevant during that phase of flight.

And it is so on take off also IMHO.

Mel said:

I know it probably uses more fuel, but it makes up by making the brake pads last longer.

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Just because the airlines do it doesn't mean it's appropriate for us. They have at least two engines, usually turbines, and therefore it's cheaper for them to burn less fuel than to take a chance on brake pad failure. It's all about the money for them.

Maybe it's just me and the fact I know Brad pretty well. But there's nothing about his post that doesn't strike me as -- how do I say this? -- Brad.

I don't usually use full power until I am off the ground and climbing, makes for an easier aborted takeoff and uses a lot less rudder force on my leg and on the rudder. Climb out is at max power. Maybe my reasoning is wrong, but this is what works for me on my taildragger.

David-aviator said:

The landing is critical. The subject of the thread is irrelevant during that phase of flight.

And it is so on take off also IMHO.

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Still having fun here Many are pretty much saying the same thing in reply?we're just giving the OPs question the respect to say why we think so, and apparently fueling a little debate and popcorn enjoyment. Heck, its finally snowing in Reno, and now I gotta wait till the roads are clear so I can drive to the hangar to work on a few new gauges that will tell me just how I can tweak the motor for even more full power on takeoff!

LMAO on the reduced power landings and taxi! Well-played gents!

Ernst, just remember, it's not a flyby?its a low approach!

And reduced power taxi?foreign concept, at least where I work!

Cheers,
Bob

rvmills said:

Still having fun here Many are pretty much saying the same thing in reply?we're just giving the OPs question the respect to say why we think so, and apparently fueling a little debate and popcorn enjoyment. Heck, its finally snowing in Reno, and now I gotta wait till the roads are clear so I can drive to the hangar to work on a few new gauges that will tell me just how I can tweak the motor for even more full power on takeoff!

LMAO on the reduced power landings and taxi! Well-played gents!

Ernst, just remember, it's not a flyby?its a low approach!

And reduced power taxi?foreign concept, at least where I work!

Cheers,
Bob

Click to expand...

Phhhsh! I have a mound of snow 4' high on either side of my drive way from all the shoveling, get to it!

Sig600 said:

Phhhsh! I have a mound of snow 4' high on either side of my drive way from all the shoveling, get to it!

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Shoveling done…for momma here and the widow next door (earning my keep…and the long leash! )

4'…now that is when you need to do a full power taxi!

By the way, I know I need to promote you here on VAF…not an L-T…but a LCDR! Have you installed the head-hinges yet?

170 driver said:

I don't usually use full power until I am off the ground and climbing, makes for an easier aborted takeoff and uses a lot less rudder force on my leg and on the rudder. Climb out is at max power. Maybe my reasoning is wrong, but this is what works for me on my taildragger.

Click to expand...

Warbirds with monster motors use less than full power for takeoff too…keeps from reversing the direction of takeoff during the roll! I'd love the have that problem! Or a 170…very nice!

Cheers,
Bob

Brake wear issue solved

Mel said:

I know it probably uses more fuel, but it makes up by making the brake pads last longer.

Click to expand...

I fly with the local CAF squadron, and we had a similar discussion about reduced power takeoffs with a R-1340 engine. Here's what we found in the T-6G Flight Handbook. (I highlighted the relevant paragraphs.)

Red Five said:

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Well, that is one way to clean out the hangar!


Military power - all the engines referred to here supercharged/turbocharged/turbocompounded or some combination. Also they are designed for high altitude, which means the turbo machinery and matches provide much more boost at ground levels than at altitude. It is easy to over boost even with 130 octane. We (mostly) are using normally aspirated engines, so much of the discussion does not apply.

Even for our NA engines, it takes about 10 min (to 15min) to thermally saturate at steady state. 5 min on TO would still allow the temperatures of pistons/top ring grooves and barrel at top ring positions to be in range and not at peaks. I think time to 1000'agl is easily within 1.0 min and should have little effect on the deleterious results of sustained steady state operation at high power/temperatures. Like - top ring groove coking, oil plating on wrist pin, marginal oil film at top ring turnaround, lowered piston fatigue strength due to elevated temps, and higher oil to bearing temperatures, detonation, and more.
Just my opinion, though.

Sorry for the diversion - continue while I get more popcorn.

Red Five said:

Click to expand...

What y'all don't realize is that this Maule isn't taking off...the photo shows it backing into the hangar (with reduced power).

rjbob said:

What y'all don't realize is that this Maule isn't taking off...the photo shows it backing into the hangar (with reduced power).

Click to expand...

I could not tell from the palm trees that there was a 5 knot head wind.

take off

Been in that hangar at Maule believe me my Champ would have been airborne coming out the door the hangar must have been 400' deep most Rv's loaded light would also.
Bob

170 driver said:

I don't usually use full power until I am off the ground and climbing, makes for an easier aborted takeoff and uses a lot less rudder force on my leg and on the rudder. Climb out is at max power. Maybe my reasoning is wrong, but this is what works for me on my taildragger.

Click to expand...

The quote from the T-6 manual that stands out to me is this:

In addition to the engine wear factor, a takeoff at reduced power is comparable to starting with approximately one third of the runway behind the airplane. Therefore full power should always be used on all take-offs.

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This makes me think of:

Things which do you no good in aviation: Altitude above you. Runway behind you. Fuel in the truck. A navigator. Half a second ago.
Approach plates in the car. The airspeed you don't have.

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Skylor
RV-8

claycookiemonster said:

1. "...reduced power take offs burn more fuel..." Really? 'Splain that to me.

2. "...reduced power is harder on the engine than full power..." So, if reduced power take offs are hard, is idle murder? As I've said before, I'm willing and able to learn, but this doesn't pass the reasonableness check yet.

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My opinion on the two above:

1. Getting to altitude more quickly with full power - then reducing throttle and leaning the mixture might actually burn less fuel versus reducing throttle throughout the take-off and climb, which would take longer (lots of variables here).

2. There is a valve (forget its name) that is opened only at full throttle on carburated engines that sends more fuel to the cylinders, thus increasing the cooling. This, of course, also varies with density altitude.

If engine wear is the concern, starting and all operation below 180 degrees temperature are the enemy. Once the engine is up to temp, engine wear is at its lowest.

As mentioned by others, any comparison to turbine engines is impossible. Their limits are expressed by turbine inlet temperature (TIT) and max torque.