What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Do you do partial power take-offs?

plehrke

plehrke

Well Known Member
Patron
I was always taught to use full power until you get to a safe altitude (typically pattern altitude). When I started to fly my RV-6A four years ago I wondered whether I really needed full power on every take-off, after all I am in the air in 500 ft, but I still use full power. Now in the cold of STL this winter I have been again thinking if I ought to use less then full power as the plane is even more peppy. Just wondering how many people use less then full throttle for take-off.
 
Why are you considering reduced power take-offs? Are you running an engine with full power time limits? Do you perceive a benefit from reduced power take-offs? Once we know your goals then we can better address your question.

George
 
I use full power always.

disclaimer: I've only got 7.2hrs on her and I'm breaking in my engine.

Soon I will be using full power until I reach 1000' then pull back to 2500.
 
Full power take

The only time I don't is when I am in a formation take off. I use full power even time with a 6000ft runway just because it is more fun and impresses the locals :)
 
Always full power unless practicing high density altitude takeoffs. But then again that's in a Piper Archer and not the RV-7 I'm working on :-(
 
plehrke said:
I was always taught to use full power until you get to a safe altitude (typically pattern altitude). When I started to fly my RV-6A four years ago I wondered whether I really needed full power on every take-off, after all I am in the air in 500 ft, but I still use full power. Now in the cold of STL this winter I have been again thinking if I ought to use less then full power as the plane is even more peppy. Just wondering how many people use less then full throttle for take-off.
Click to expand...

Altitude is my friend :). Yes, full power, full rpm till 1000', then 2500rpm WOT till cruising altitude. IMHO it's safer to get up quicker, and it's certainly more fun! :)))))).
 
As the old adage goes, the most worthless things to a pilot are runway behind you, altitude above you, and fuel in the truck.

Most airlines use partial power take off's 90% of the time. I'll vary how much power I use for what I fly at work based on conditions.

That said, those are multi engine a/c. If we accept that we're in a single engine a/c and remove engine out considerations, then yes for longevity you can probably lengthen the life if your engine by minimizing your use of full throttle. However if you're doing a reduced power takeoff, and cruise climb to cruise alt you're almost guaranteed to burn more gas than to use full power to altitude, where you can get back to a cruise power setting, speed and fuel burn sooner. Try testing it out some time. Do a reduced power take off and cruise climb to say 10K', and see how long it takes and how much fuel you burn. Then do it again with full power and a Vy climb to 10K. Curious to see the results if anyone tries it out.
 
sjarrell said:
Altitude is my friend :). Yes, full power, full rpm till 1000', then 2500rpm WOT till cruising altitude. IMHO it's safer to get up quicker, and it's certainly more fun! :)))))).
Click to expand...
I agree with the more fun and get to safe altitude faster. Of coarse everybodies situation is different (short field etc) but I fly out of an airport that is under the 1700 ft level of a Class B. Therefore I can only climb 1000 ft and then have to level off and fly 5-10 nm before I can start a slow climb until clear of the Class B.
 
On many piston aircraft a slightly reduced power takeoff is potentially harmful because you do not engage the full power enriching that provides extra cooling fuel on the slow, high power pull on takeoff. A fully loaded pig 172 at sea level on a hot day, fixed pitch, way over square limping into the air with little cooling air and a throttle pulled back 1/4" with CHTs climbing through 400f is a perfect example of why it is often taught not to do partial power takeoffs in a piston acft........

...... However, this is NOT the senario with most RVs; Most are so nimble they can takeoff with a very significant power reduction and not create CHT cooling issues as described above. Is this easier on the engine? Yes. Will the engine last longer? Perhaps not. Most RVs might rust out before they wear out. Will this save gas? Depends. One thing I have noticed using a lot of all around reduced power ops is the oil gets dark faster. I'm not sure but perhaps extensive use of reduced power (all around) is making the oil get darker faster because the rings are allowing more blow by with less pressure? Any gurus on this one?
 
Every takeoff. We have a very rough (many pebbles) first 500' of runway that will chip your prop/plane if you go full throttle. My takeoffs to the south involve a VERY gradual increase in MP over the course of about 8 seconds, and of course by the time I get to around 19 inches I'm in the air. Usually not to 25/25 until about 50' agl.

plehrke said:
snip...Just wondering how many people use less then full throttle for take-off.
Click to expand...
 
Last edited:
Full Power

I am brand new to the forum and anticipate building an RV 7 shortly, but in
response to the question concerning full power takeoff's and the airlines.

Jet engines are capable of producing more than 100 percent power on takeoff and that is the only reason that power settings for N1 are reduced to keep from exceeding 100 percent power but we always use 100 percent power on takeoff. Like some stated in cold weather yes since the air is less dense the aircraft climbs like a cat on fire.

Being a flight instructor for many years you'll also find out that in some piston aircraft especially those turbo charged you'll use a reduce MP for the same reason.

the post concerning gravel... I would do the same but eventually in the takeoff roll Full power would be used till either reaching a safe altitude or a specific time reduction by the engine manufacture for continuous power.

In breaking in engines Most recommend using full power take offs and cruising between 75 and 65 percent and no quick power reductions. You want to set the rings and pressure is the only thing that sets them. If you don't set them correctly you'll end up using oil and eventually replacing the jugs and breaking them in again.

I hope this helps consult your breakin schedule on your engine. that is the best source since they are supplying the warranty on it.

Smilin' Jack
 
Sig600 said:
However if you're doing a reduced power takeoff, and cruise climb to cruise alt you're almost guaranteed to burn more gas than to use full power to altitude, where you can get back to a cruise power setting, speed and fuel burn sooner. Try testing it out some time. Do a reduced power take off and cruise climb to say 10K', and see how long it takes and how much fuel you burn. Then do it again with full power and a Vy climb to 10K. Curious to see the results if anyone tries it out.
Click to expand...

You need to take into account the down range (missile term) distance as well to see the benefit of a cruise climb. I planned a simple cross country (in weathermeister so todays weather has me flying into a 35kt head wind) cruising at 10Kft using my perfromance numbers for a 6A with 180hp and fixed pitch 85" Sensenich prop.

for a 80 nm trip
max power 80 kt climb: 42:30 mn flight and burn 7.1 gal
max power 130 kt cruise climb: 39:31 min flight and burn 7.0 gal
part power 120 kt cruise climb: 42:52 mn flight and burn 6.5

for a 180 nm trip
max power 80 kt climb: 89:02 mn flight and burn 14.5 gal
max power 130 kt cruise climb: 86:11 min flight and burn 14.4 gal
part power 120 kt cruise climb: 89:34 mn flight and burn 13.9

Looks like max power cruise climb saves time and part power (75%) cruise climb saves gas but your numbers may vary.
 
Last edited:
Philip
For most of the flying I have done in 40 years... it has been fly fast into a head wind and use the tail wind to conserve fuel. Lot of studies out there and the end results are basically the same. Altitude has a lot to do with it also and possibly taking an off track to put the wind on your side will help your ground speed.

Smilin' Jack
 
Partial power take-off? NEVER!

I've been flying off of gravel runways since 1967. Even flew a Mooney (noted for minimum prop clearance) off gravel for over 2 years. Never chipped a prop. The secrete is to never apply full throttle while the aircraft is sitting still. This is what picks up rocks and debris. Feed the throttle in slowly at first. Once the aircraft has traveled 75' or so, you are moving fast enough that the prop should not pick up anything off the ground. By that point, you should be at or close to full throttle. From that point, I always use full throttle
at least until clearing all obstacles.
 
I take off with less than 100% power almost every flight. Someone determine my power setting at 7000' density altitude and 2200 RPM.

Since I feed in throttle slowly, at sea level I am probably airborne before full throttle.
 
always full power

In my mind, one of the most dangerous flight regimes for an engine failure is between liftoff and untill you get to an altitude where there are some engine out options.

Full power gets you through that flight regime the quickest.

I don't want to lollygag around at 70 knots 100' - 500' any longer than is absolutely necessary.

As someone else asked "what are you trying to gain by less than WOT takeoffs"?? I really do not think full power hurts a properly rigged engine. Burns a bit extra gas.

Can't think of a good reason not to go WOT.
 
I'm pretty sure that the original poster meant "maximum available power"!
 
I always use full throttle but at my base airport at 5,800' (KAPA) never produce full power. That said, even at airports below sea level, I use full throttle. Unless the runway is very short, I add power gradually (approx. 5 seconds).
 
My 15 year old son has just started doing takeoffs. He has a tough time with keeping the plane straight upon application of full power so he starts slowly increasing throttle to minimize the jump left tendency. I'm slowly breaking him of that habit.
 
In my mind, one of the most dangerous flight regimes for an engine failure is between liftoff and untill you get to an altitude where there are some engine out options.

Full power gets you through that flight regime the quickest.
Click to expand...
Ahhh... but this assumes that P of an engine failure is the same at full and reduced power settings ;)

One of the original benefits of reduced power takeoffs in the airline world was to reduce engine wear / chance of a failure. No idea of the numbers...

One of the main reasons to do a reduced power takeoff in GA is less noise. More practical with a C/S prop - limiting RPM to say 2500, or 2400, reduces noise a lot, provided you are happy with the lower power... you will find some strip owners making it a condition of using their strip if they are "neighbour concious".

Andy
 
plehrke said:
You need to take into account the down range (missile term) distance as well to see the benefit of a cruise climb. I planned a simple cross country (in weathermeister so todays weather has me flying into a 35kt head wind) cruising at 10Kft using my perfromance numbers for a 6A with 180hp and fixed pitch 85" Sensenich prop.

for a 80 nm trip
max power 80 kt climb: 42:30 mn flight and burn 7.1 gal
max power 130 kt cruise climb: 39:31 min flight and burn 7.0 gal
part power 120 kt cruise climb: 42:52 mn flight and burn 6.5

for a 180 nm trip
max power 80 kt climb: 89:02 mn flight and burn 14.5 gal
max power 130 kt cruise climb: 86:11 min flight and burn 14.4 gal
part power 120 kt cruise climb: 89:34 mn flight and burn 13.9

Looks like max power cruise climb saves time and part power (75%) cruise climb saves gas but your numbers may vary.
Click to expand...


I love it, question to data in no time flat.

I really thought the fuel burn difference would be bigger. Less than a gallon over a 180nm trip is surprising for the variables.
 
Not RV but...

...one of the C185 owners at my local club insisted on reduced power takeoffs to save gas, ended up paying for an overhaul to fix the glazed bores that resulted.

Given the cost of the remedial work as compared to the gas savings by not going full power, this strikes me as false economics (or going broke saving money!) :)
 
How did you determine that was what caused the glazed bores?

sjjonesnz said:
...one of the C185 owners at my local club insisted on reduced power takeoffs to save gas, ended up paying for an overhaul to fix the glazed bores that resulted.

Given the cost of the remedial work as compared to the gas savings by not going full power, this strikes me as false economics (or going broke saving money!) :)
Click to expand...
 
Only when practicing high-DA ops, and I don't think I've done that since my primary training.
 
Saving Gas?

There isn't much fuel savings available in reduced power take-offs. How long do you spend at full power before reducing for the climb? Even at 16gal/hr full power vs more time at 12gal/hr, there is very little fuel to be saved.

If you really want to be frugal, and perhaps easier on the engine, I would set the prop at 2500 or 2600rpm.

The only valid reason I see is formation take-offs and non-paved surfaces.

Back when I was doing my float rating, they used 172s. Take-off and climb were both at full power. The prop was pitched for 2700rpm at 80mph, and that was how you climbed. You wouldn't dare compromise the rocket ship-like 400fpm climb by reducing power at all. Now because the prop was pitched so fine, the cruise was a mind boggling 90mph at 2500rpm. I have no idea if the engines made it to TBO, but as a business, if it didn't make economical sense, they wouldn't operate that way. Their high time 172 has 40,000 hours on it since they bought it new, so I don't doubt their logic.
 
You must log in or register to reply here.
Back
Top