Less than full power takeoffs?

[Pace]

Don't think this has been brought up for discussion so am interested in other opinions.

We are taught and conditioned into full power takeoffs.

On a long runway I tried an experiment with a seneca five twin and applied the climb setting rather than the takeoff setting. Ok I had a massive runway but the takeoff was smoother and quieter for the PAX, the aircraft took off and there were no power changes and straight into a a climb setting.

Ok this was In a twin and I realise the takeoff distance would not match the manual, engine failure? Just shove the levers to MAX but the whole thing was silky smooth for the PAX.

Have others tried less than max takeoffs on long runways ?
Larger aircraft do this so I was just experimenting :ok:
it will reduce the strain on the engine but only on long runways

[9 lives]

I have done less than full power takeoffs many times, for varying reasons. In my flying boat I found to my surprise, that with some careful handling, I can takeoff, fly, slow to descend from within ground effect (water really), land, and takeoff again, all at 19" MP, without touching the power. Doing that is just a skills thing. Other takeoffs are partial power just to be nice to neighbors, particularly on lakes, both wet and frozen. Flying single pilot turbine, I have done partial power takeoffs to prevent having to very carefully set power during the roll in a tight runway. There's always more power if I push the power lever, so if partial power is trouble and worry free for over temp/torque, so much the better. Better eyes out on the road! Last, and fearsome, there are some higher performance single taildraggers, which are going left off the runway, if you open up the power at an airspeed below that in which the rudder has effect. Partial power until the rudder rudders!

[piperboy84]

If I have a long runway and nobody else is around, I put partial power in on the Maule lift the tail and go down the runway going faster then slower practicing balancing on the mains then full power 500 feet from the end. It's a lot of fun.

[UV]

The original poster is asking about a Seneca 5, so the first question has to be ..."is this a Public Transport Flight?"

Assuming it is PT then you need to ask yourself...
Is it permitted in your Ops Manual? Probably not mentioned at all.
Where would you get the Take off and Climb Performance figures from?
Would the CAA be happy with the extended exposure at low level?
Would they be happy with... "engine failure? Just shove the levers to MAX"... after an engine failure?!

So, off the top of my head, I'm sure its a non starter for Commercial Ops.

For Private Flights ...well I don't know! What does your Flight Manual say?

[Consol]

Folks, Australia's CASA published an article on same some years ago (10+). Quite conclusive that it is NOT a good idea for many reasons. Google it.

[9 lives]

What does your Flight Manual say?

Good point, I had a look...

One of the types I was referring to says:

"Gradually advance power lever, keeping the stick fully rearward until required RPM is achieved........ Normal takeoff may be accomplished at a lower power than the maximum allowed"

The Caravan says:

"Power - SET FOR TAKEOFF (observe Takeoff ITT and Ng limits). Refer to Section 5 for takeoff power". The Section 5 "ENGINE TORQUE FOR TAKEOFF" table states 1900 RPM, and provides a table "area" which includes a large range of power within torque and temp limits.

A few piston types I know (C 182, for example) are RPM limited for noise abatement by STC, so they are not developing full power at takeoff, using the Flight Manual procedure.

Others I checked do say "Full throttle" for takeoff.

[Big Pistons Forever]

Every single engine piston POH that I have specify "full throttle" for takeoff and for those with constant speed props, the max RPM.

A reduced power takeoff is therefore not an authorized procedure.

Personally I think it is a bad idea in a SEP because in the event of an engine failure. altitude = options. So a reduced power takeoff means that you will not be as high as you could have been at every point in the take off flight profile.

I think it should also be noted that virtually every carburated and fuel injected piston engine is designed so that it has an extra rich mixture at full throttle. Therefore the engine could will run hotter at a high but not full throttle setting. This is particularly significant with turbocharged engines

[skyhighfallguy]

I echo big pistons forever, esp about cooling with extra rich mixture.


BUT for the Seneca V driver. How about this: you do a reduced power takeoff (climb power) and you lose an engine.

Do you add power on the good engine?

I'll bet you would have to. BUT IF YOU WERE ALREADY at full takeoff power, you would simply have to feather the bad engine, instead of moving throttles around.

[BackPacker]

Every single engine piston POH that I have specify "full throttle" for takeoff and for those with constant speed props, the max RPM.

Actually, no, not quite. I fly the GA8 with an IO-540. Takeoffs are done using 2500 rpm. In fact, 2500 rpm is the limit for all operations, except emergency. There is a detent in the blue lever that lets you get past 2500 rpm, but that travel range is marked for emergency purposes only.

2700 rpm gives about 30 more HP, but also considerably more noise. And that last thing is the reason for all this: All performance figures, including the noise measurements/certification, are based on 2500 rpm. With 2700 rpm allowed under all circumstances we would not be able to get the advantageous noise certificate we have now. Which significantly increases landing fees at some airfields.

But again, this is an exception. I do not know any other aircraft that has a reduced power setting as default in its POH.

[Pace]

BUT for the Seneca V driver. How about this:

The seneca Five is unusual compared to the Earlier Senecas in that the engines are turbocharged supercooled and waste gated and can use maximum continuos power.

the earlier Senecas were not and max power was time limited to five minutes
Let me put this question? After take off and having cleaned up the aircraft you would normally go to a climb power setting anyway so what happens if you loose an engine then? You would advance on the good engine or maybe on both until you had identified the problem engine and if you still had power from it, that procedure takes a fraction of a second.

In my engine failure in a twin (reported here) which happened at 200 feet agl do not be too hasty in shutting down and feathering what maybe an engine still supplying some useable power.

i estimated 30% from a violently shaking and yawing aircraft so instead put my hand on the prop lever ready to feather and used that 30% until a safe height then shut it down. Had I shut down and feathered I would have without doubt ended up crashing.

I think its the Aerostar( Machen) where engine failure requires a reduction of power on the good engine because the rudder could not hold full power and many engine failures resulted in loss of control.

Some powerful single turbines and pistons required reduced power because of torque and lack of rudder authority at slower speeds in the takeoff roll with further power added at faster speeds and more rudder authority ?

I opened this thread up not to promote less than full power takeoffs but to discuss them and less than full power operations when full power maybe your instincts

[notjustanotherpilot]

The only time I've used less than full power was while taking part in some advanced training (Mooney pilots proficiency program)and the instructor decided that the conditions which happened to present to us (wasn't planned) would be a good demonstration of hot and high at mtow.
We knew we would get off the ground safely and with room to spare but it was a very good demo of just how much extra tarmac was required and the very leisurely climb rate.

[Desert Dawg]

Where is Adam Frisch's opinion? He used to fly the Aero and can shed some light on this from his experience.

[Pace]

Desert D

Not sure whether it was all AeroStars or just the more powerful Machen conversion? But I am pretty sure all of them were a handful engine out and required a reduction on the good engine? i have never flown one of those quick birds ;)

[Above The Clouds]

I have quite a lot time in the Aerostar 601P, the single engine handling was interesting but not as bad as rumours state.
Of course in any multi engine aircraft you always have the option to reduce power on the operating engines to maintain directional control even if that means landing ahead under control.

Anyway as the OP said let's discuss the reduced power take-off.


Skyhighfallguy
I echo big pistons forever, esp about cooling with extra rich mixture.

BUT for the Seneca V driver. How about this: you do a reduced power takeoff (climb power) and you lose an engine.

Do you add power on the good engine?


Your first action during such a failure should be to confirm or apply full power to all engines anyway.

[S-Works]

We never do full power takeoffs even at max weight. A light weight take off is 45-50% and a max weight will be 55%.

In the event of an engine failure we also do not go to full power on the live engine, its 'power as required' and in a light load aircraft we generally don't need to add any. Fully loaded we might add 5%.

[Alteburger]

I have found these articles excellent background reading

Pelican's Perch #63:<br>Where Should I Run My Engine? (Part 1) - AVweb Features Article (http://www.avweb.com/news/pelican/182179-1.html)

In turbines, reduced power takeoffs are the norm of course but, piston engines may not respond so well. In my experience operating old supercharged radials, it was recommended particularly to use full power for takeoff as the extra fuel provided significant cooling to the engine. I'm definitely no mechanical expert and read as much as I can to try and find the best operating methods for safety and engine longevity, but found this series of articles very plausible.

[Big Pistons Forever]

Desert D

Not sure whether it was all AeroStars or just the more powerful Machen conversion? But I am pretty sure all of them were a handful engine out and required a reduction on the good engine? i have never flown one of those quick birds ;)



I have 500 + Aerostar hours. All Aerostars, including the Machen ones have a certified published VMC speed. This speed is below blueline for all models at all weights. If you are in any twin and flying below VMC you are going to have to reduce power on the operating engine.

If you are in this situation in an Aerostar anywhere close to the ground you are going to crash as this airplane will go nowhere but down at any speed below the (very high) blueline speed

[ChickenHouse]

Interesting, I just checked a 1967 POH for a 172 - full-throttle is only set to check at run-up, not written down for take-off. Only for max. climb rate full throttle is required. Any idea why Cessna decided to not document throttle setting for take-off, freedom of choice?

[The Ancient Geek]

No idea, I have always used full power.
There is nothing more useless than the runway behind you.

[Pace]

If we take that the performance data is established from max power ( Not on all types of singles) then going away from that and using less than max power and the takeoff roll and initial climb will be degraded to an unknown factor.

Some high powered singles with a lot of prop torque effect require a lower power setting for the initial take off increasing that power as more air flows over the rudder.

That then beggars the question on lower powered singles do you stand on the brakes releasing them on achieving max power or smoothly increase to max power as speed increases. One is smooth the other much more frenetic for your passenger

Do you stand on the brakes regardless of whether the runway is short or long.

Sometimes in the past there has been an aircraft on finals! ATC ask you to expedite your departure as you enter the runway from the taxiway! Do you taxi out stop and line up on the numbers, hit the brakes and build to max power or start your takeoff slowly increasing power while in a turn to the centreline? :E to assist separation to the landing aircraft?

i have seen that done by more experienced pilots many times in large jet aircraft as well as small aircraft too! To be shunned on ? accelerating on the turn to the centreline? i.e. do you ever start your takeoff roll while entering the runway from the taxiway? Not advisable with max power so theoretically a reduced power takeoff

[Maoraigh1]

Is there a temperature producing a very low density altitude at which full throttle will produce too much power, over stressing some engines?
PS Adding power as you turn onto the runway, with no stop on the runway - soft ground?

[Jetblu]

Nah. For take-off I'm looking for maximum available manifold pressure and RPM every time.

[chevvron]

My first flight deck ride in a Tristar, I noticed they set the thrust at 80% for takeoff and never went above that. '146s have a computer which calculates how much thrust you need according to auw and limited the thrust accordingly.

[Silvaire1]

A lot of people in a lot of planes make take-offs at less than 100% power: at a high DA airport you can only get partial power from a normally aspirated engine.

[Big Pistons Forever]

A lot of people in a lot of planes make take-offs at less than 100% power: at a high DA airport you can only get partial power from a normally aspirated engine.

The generally accepted definition of a "reduced power takeoff" is one where the pilot deliberately chooses to not set the power/engine controls to produce the maximum power available.

[Pace]

BP

The Spitfire was like that you had two settings on takeoff one reduced for the initial roll and a higher setting when there was more control authority

[UV]

Sometimes in the past there has been an aircraft on finals! ATC ask you to expedite your departure as you enter the runway from the taxiway! Do you taxi out stop and line up on the numbers, hit the brakes and build to max power or start your takeoff slowly increasing power while in a turn to the centreline? to assist separation to the landing aircraft?

i have seen that done by more experienced pilots many times in large jet aircraft as well as small aircraft too! To be shunned on ? accelerating on the turn to the centreline? i.e. do you ever start your takeoff roll while entering the runway from the taxiway? Not advisable with max power so theoretically a reduced power takeoff

ATC would expect you to take off immediately without stopping on the runway. If you are going to do something else then you must tell them (which may waste more time) so better still decline the offer. All explained in CAP 413...you know... the RT Manual!

[Ampage]

Extra 300 - levers to the wall.. and it goes like **** off a shovel.

Where's the fun in using less power? :D

;)

[Pace]

Where is the fun ?:E I think many of us have experienced the extremes in flying from severe turbulence to storm penetration to severe weather landings, go arounds from missed approaches etc.

Carrying PAX and you have a different challenge as most PAX are nervous of flying or want as smooth a flight as possible and that then becomes the challenge.

You avoid the lumps of cumulus, change levels to get out of upper air turbulence and do everything possible given the conditions to make the flight seamless.

building to maximum power against the brakes and then being pinned to the seats by the acceleration might be great for us but not so great for nervous PAX
Ok short runway you have to do that but do you have to do that on a Heathrow type runway.

Hence that " experiment " on a very long runway with a Seneca Five and a takeoff with cruise climb setting. the takeoff roll was smooth the climb smooth with no power changes until cruise altitude . Ok it was just an experiment and not a modus operandae

[Another St Ivian]

For big planes, typically anything much larger than mid-size business jet right through to 747/A380 size, there will exist a fairly healthy margin between the engine thrust/power needed to get airborne and climb out and a healthy rate, and what the engines can deliver with the power levers wide open (for most conditions!). In those circumstances it doesn't make a great deal of sense to thrash the engines, and can indeed make life safer all around if you use just enough engine-ooomph to get up and away.

For those scenarios there is a fairly well trodden path, and it goes something like this...

As a previous poster alludes to, quite often an aircraft will happily take-off from a runway for a large range of ambient temperatures. However when the ambient temperature increases, a number of things happen: the engines typically generate less thrust, the density altitude increases, the IAS/TAS split becomes larger, and so on.

When a large aircraft manufacturer certifies an aircraft, they will conduct a large number of take-off and climbs for a large range of conditions. They will then further in the background take that data, identify trends, and sensibly extrapolate out until you now have a data-set which can tell you exactly how an aircraft will behave for any given runway, OAT, wind, slope etc.

So, back to the day where we're sat in the cockpit, we don't have many passengers, the aircraft is light, and we have a really long runway to take-off from. How much thrust/power is just enough? Well we can play a little thought experiment here: If I used the runway I'm on today, what in theory is the hottest ambient temperature I can successfully take-off with? Fortunately my voluminous data set from the aircraft manufacturer can go through all of those factors and arrive at answer: ASI, you could take-off today up to 45 degrees celsius, say.

What I can then do is consult my engine data and ask; at 45 degC, what engine setting am I going to get? Typically for jet engines this is measured by engine fan-speed (N1), or engine pressure ratio (EPR). I might find out that on a 45 degC day with the throttles wide open, the engine will give me 91% N1.

But it's actually really cold out today, say only 10 degC at the airport, what good does that nugget of knowledge do for me? Well what it means is I can push my throttle forward to get the 91% N1, and the engines will give me just enough thrust to get off the runway and climb away. I have in effect lied to myself about the temperature, and set the engines to a lesser thrust than they could otherwise achieve with full power in today's colder weather.

This approach all in all is called a FLEX derate, and is relatively common amongst Boeing and Airbus (barring differences in terminology). The success of this approach is based on the following things: A really expansive and well validated set of data from the manufacturer, some very accurate engine gauging and predictable engine behaviour, and a rigorous set of SOPs to make sure that the soft and squidgy chaps up front input the right numbers, get the right numbers out, and apply them correctly.

Coming back to the average light aircraft...well, you're basically out of luck on the first two counts straight away...

[9 lives]

Carrying PAX and you have a different challenge as most PAX are nervous of flying or want as smooth a flight as possible and that then becomes the challenge......

building to maximum power against the brakes and then being pinned to the seats by the acceleration might be great for us but not so great for nervous PAX. Ok short runway you have to do that but do you have to do that on a Heathrow type runway.

Very true, and a good reason to practice gentle handling - nothing sudden, or "full" if it can be avoided.

When I started right seat in the Cheyenne in the '80's, I was sharply told by my Captain: "Hey, the people back there are paying for this ride, they want a smooth one!"

In the last two days I have been doing the initial proving flying for a new amateur built "Cessna 172" taildragger, with 180HP, and extended STOL kitted wings. The first takeoff I eased the power in, and found I was airborne before I had eased it all in! Apparently it did not need full power to get airborne in a few hundred feet! I did learn to use full power though, and found a sustained 1300 FPM rate of climb - certainly a first for me in a 180 HP 172!

[foxmoth]

Harvard we used to use reduced power unless on a shortish runway, VERY noisy on full power!

[Pace]

ASI

A very well and informative response. I fly business jets and agree totally with you.
We check the temp and airfield elevation and take the N1 setting from the book normally in the Citation about 97.4% N1.
Yesterday at the airfield I departed 28 C and 1000 ft ASL it was 96.2 N1. You can build on the brakes to that thrust setting and let go or apply that thrust setting progressively which is smoother and not so greyhound out of a trap departure. Jet engines do not have the torque effect that piston and turbine singles can display.

Obviously that then meets the takeoff performance charts. Anything less and you are in the relatively unknown.

Changes in jet engine thrust are not so noticeable to PAX as they would be in a piston single or twin where RPM and manifold changes are more noticeable especially in twins where out of sync can mean an alarming sound to unknowing PAX.

Maybe Paid to fly and flying PAX your goals change? As few turns as possible as smooth air as possible as slick and time saving as possible? Etc

That becomes the challenge not the excitement factor.

But that emphasis can be the challenge flying PAX in light singles and twins to make the operation as smooth and slick as can be.

My experiment was just that! An experiment on a long runway and have to say it was very smooth :ok: But not something i am advising.

We are so conditioned to go MAX and that brings in other considerations where going MAX can be fatal. you only have to go and look at the stall spin accidents on high powered single turbines like the TBM series or aircraft on go around or low and slow or look at high powered singles which will not take MAX on takeoff so in a way maybe this is just to be aware that Our training on low powered pistons is not the best on higher powered aircraft.

How many accidents have occurred where pilots are so brainwashed to max power that approaching VMCA in a twin they do not consider reducing power on the one live engine because they are brainwashed to MAX is best