Pitch full fine??

[Poita]

An operational query...


Just wondering what everyone does out there in regards to pitch levers? Do you go full fine on finals or leave them where they are?

Also while we are on the topic how about mixtures on descent and in the circuit? Do you enrichen on decent or leave them as is...and do you go full rich in the circuit??

If you have any input please state what aircraft you are doing (or not doing) it in.



So many questions....

[foxinsox]

I guess that depends on your training really.

I've been taught to ensure prop is full fine on final in case a go-around is required (max thrust capable).

Mixtures.... I've been told it's not worth running lean under 5000' simply because the benefits are not outweighed by the dangers of engine damage, so I am usually running full rich in the circuit, and most days under 5000' (unless at YSCB, depending on the day). I too am curious as to others techniques for descent.

This info only relative to C172RG, not into bigger machines yet.

[high talker]

i've always gone pitch full fine on final as part of the PUF checks done this on all aircraft flown up to a PA31. I also believe this is a wise move as it is one less thing you need to do in a go around.

[Piston Twin]

Pitch to climb power setting. Mixture full rich in circuit and slowly increased on descent. Aircraft type Cessna 340. Most other aircraft pitch full fine on finals and mixture full rich. :D

PT

[GW_04]

Pitch full fine?

Absolutely. It does not matter if your in a turbine or a C182.
Power is a function of torque x RPM. If you have full throttle in a piston or max torque in a turbine it is not going to be any where near full power unless you have max RPM.
The time you need full power for landing is not normally for a go around as often as it is to arrest your rate of decent when landing on a shorter strip with reduced speed when you encounter a sudden wind shear (sink) with a full load.
Trust me... the day you NEED full power on landing you will s**t your self if the pitch isn't fine.
As for mixture, its all good to have full rich in the down wind incase you need that full power. In decent, if you have an EGT it is wise to maintain your cruise EGT setting during the decent by a gradual en-richen, that way you wont make any large changes in cylinder head temp (ie. shock cooling!).
Going to full rich on decent with an increase in airspeed is only going to cool your engine to quickly creating un-neccesary torsional stresses on your engine.
Hope this helps.

G :ok:

PS: from my past bar talks and experiances, the best way to crack cylinders in a piston, is to let the engineers do ground run ups with the cowls off! Dont let them!

[currawong]

Short finals - pitch full fine

Mixture - enrich in increments on descent

Depending what you fly, best power ie take-off may not be full rich

Some A/C are placarded or have a chart in the POH as to what fuel flow (mixture) at full throttle you require vs altitude for maximum performance.

Meaning, as soon as you have full throttle on the T/O roll, the mixture should be adjusted back to best power fuel flow for your altitude, if required.

This placard has info for sea level, 4000 ft, 8000 ft for instance.

Meaning, you can lean, at any altitude, including sea level

If in doubt, check the POH - there are folks out there that do not, who swear by time honoured methods that are basically incorrect and expect everybody else to do the same.

[GW_04]

PS...
I suggested, to try to maintain cruise EGT in decent! Sometimes this maynot be possible due to reduced power setting,....so try to stay 50 to 100 deg. RICHER of peak for the power setting.
Cheers. My 2 cents worth. ;)

G

[0tter1]

Full fine for landing, a good idea! However how you do it is another thing. Its painful to hear people on short finals ramming the pitch controls forward giving the governer a good run for its money. Which can also make the passengers a little uncomfortable, a sudden increase in noise, and deaccleration. Good airmanship always stands out and will always help you along your way. Whether you are trying to impress your testing officer, or a big breasted passenger from Norway.

As for leaning, agree with GW. Doesnt hurt to maintain the cruise egt (or slightly richer) on the decent by enricening mixture to maintain the egt. Can always refer to the POH for the a/c you are flying. Some engines are more prone to shock cooling than others (continental!!) If you keep it too lean can lead to burnt out valves. To rich can lead to rapid cooling and subsequent cracking. Gotta love turbines, power lever to idle, and point the nose at the dirt!! Only cracking you have to worry about is your eardrums!

P.S GW_04, I recall the bar talk on many occasions. :ok:

[Tinstaafl]

Gradually enrichen during descent. Full rich as part of pre-landing checks UNLESS I'm using carby heat. In that case full rich after c/heat off.

Crz RPM during the descent & approach. After speed is reduced/full flap selected & the throttle is now controlling RPM ie prop is on its fine pitch stops, then I select Max RPM. Usually occurs about 300' or so. Avoids having an increased RPM racket & gives the mechanism an easier life.

Max RPM is needed not for the go-around but for the suddenly needed squirt of power during a slightly misjudged or gust affected landing. Plenty of time to move the knobs for a go-around from final.

[GW_04]

Tinstaafl

Love your work mate. You cant put it much better than that.

;) G

[swh]

Poita,

Depends on the aircraft, something like a PA31 the POH has EGT guidance on descent, generally speaking if you are reducing your power 1"/minute in descent you will be under the limit.

You should also enrichen mixture gradually, as more POH guidance is not more than 50 deg egt rise rise per minute. Enriched from cruise to full rich can have a 100+ deg EGT drop.

This is just basic looking after the turbocharger and pistons stuff.

Props, depends on the A/C, something that has geared engines like a 404 will not like going full fine on finals, gearbox goes places, PA31 used to leave the props where they were for cruise/descent until on finals and the props/engine was out of the governing range, go full fine and you done get a noticable sound pitch change.

If you are going to go around M up P up P up so you got it covered anyway.

GW_04: turbines I have flown have had climb RPM for the circuit, not takeoff, eg B200 1900 RPM climb/approach and 2000 for T/O. Garetts are a little different.

[Speeds high]

I hate to be a spanner in the works but...just for intrest

One current aircraft type, pitch's to Climb setting, as the very slow governer will not be able to handle sudden full power and an overspeed will occur.

Its been a while since ive flown a 172RG but as i remember the engines are very oilley, same as the duchess, i think we would lean at all times to stop the plugs from fouling, even below 5000 feet (particully on the ground) and enrichen slowly in descent.

Im sure someone will speak up if im wrong as its been a while.

:ok:

[scramjet]

I beat this question to death a couple of years ago- see the discussion here

Pitch Full fine on finals (http://www.pprune.org/forums/showthread.php?s=&threadid=21540&highlight=Pitch+full+fine+on+Finals)

Other than that do what the POH says- And I promise you if the POH does not agree with what you are being told then they are telling you old wives tales and you are on the road getting your fingers burnt- their has been many times yours truly has taken some extremely experienced person's word for gospel only to find out later that it was wrong! Its slower and takes longer but read the books for your self and you will never regret it.

IMHO anyway
:D

[GW_04]

swh

You raise an interesting point there. A little out of the scope of my knowledge though.
With my experiance with the Garett, yes you are correct in that it is even more important for the RPM to be up given that its a fixed turbine and you wont get the airflow needed to create full power.

Why does the type you specify require different RPM's for the approach as apposed to T/O. Is it a vibration thing? Is it to do with keeping the blade angle above beta range in flight? Does a go around suggest the same RPM as approach?
Interested.
Most of my experiance is with the PT6, and I know that a different pitch/rpm configuration can have drastic effects on approach handling.
Would like to know more?

Thanks
G

[fitternturner]

Full fine before landing is very important in a PT6 if you want Beta/Reverse to work properly.
Unless the prop is on the beta nuts (ie: out of the governed range and at the primary blade angle) you won't get beta as you expect it.

[Sheep Guts]

Fitter,
Very true. But really allot of different operators have different ideas about this subject. I flown Otters on both sides of the globe and the teachings are very different. The company I worked for in the N.T. Declined to go to full fine until either on the ground for a long landing only and normal landings were as you specified. Also King Airs Ive gone to 2000 RPM prior to touch down then full fine on the ground. D ifferent companies diff SOPS :{ . Thats life in the aviation. But if I was in a recip I would go full fine ie, PUFF, MPFG, prior to landing allways.


Sheep.

[swh]

GW_04,

Don't know the answer to your question, the factory SKA B200/B200C checklist has Propellor Lever - Full forward as part of the normal land and maximum reverve thrust landing checklists. These checks are conducted after the "before landing checks" and before the "balked landing" or "after landing checks". This is also the same on the factory B1900 checklists.

The factory Cessna 441 checklist has condition levers, Takeoff, Climb, and Landing as part of the before landing checks. I dont have my metro checklists handy, but I think it was the same.

Would not be surprised if keeping the RPM low is so people dont put the aircraft on the back when doing single engine work, the engine being so derated, on the 1900 normal torque is about 3400 ft-lb, but if you go full power (870 ITT for 20 sec) you can get 5000 ft-lb, that is almost a 50% increase, when single engine that is bad news.

[The Bullwinkle]

I have always selected full fine on short finals in case of a go-around.

PN68, C-310, AC-50, PA-31, BE-55, BE-58, BN-2, DHC-6.

The twin-otter requires full fine so that reverse can be selected on the ground.

[swh]

Bullwinkle,

Full fine is required for reverse with every PT6 I can think of, but even with the twotter I would thave thought you could go full fine after touchdown.

[Sheep Guts]

You right swh. And others have just highlighted that the PT6 is full increase before landing. But the problem there in lies with different operators that teach different ideas. Which is dangerous. I had to travel to the Carribean to learn how to fly Otters properly. The training I recieved in Oz was poor, From my post above you can see why. One needs to adhere to the POH of every type and stick to their findings.


Sheep

[The Bullwinkle]

swh

You are correct, however it depends on your type of operation.

My experience was in the Torres Strait, and as an example, landing at Darnley Island (400metres) on a nil wind day, it is a good idea to have reverse immediately available on touchdown.

I would not have liked to land, take my hand off the power levers, select full-fine, then go back to the power levers to select reverse.

[splatman]

Sheep is 100% correct, in that different operators have different SOP's. Like sheep I have flown for company's that have required props to full fine on landing and conversley those that require full fine by 400feet with a stable approach.

Both sets of SOP's were satisfactory and safe with the appropriate 2crew coordination. (ie the PNF selects the prop levers to max on touchdown or on the call of going around) I would note that the company selecting props to max on the ground were operating in runways a minimum of 1500m.

Intersting discussion about the requirement for the props to be at max before you are able to select beta or reverse. ie someone said "Unless the prop is on the beta nuts (ie: out of the governed range and at the primary blade angle) you won't get beta as you expect it."

All of the PT6's I have flown (-20, -27, -34 and -45R) have had an interlock mechanism with the prop levers to prevent selection of beta or reverse unless the props are selected to max, this was a safety mechanism compliments of the manufacturers to prevent inadvertant selection in flight. So simply put unless the props are at max you can't selct the power levers below flight idle.

There may be variances out there that I havn't had experience with that may allow the selection of beta or reverse with prop levers at min.

If the interlock mechanisms were removed then selection of beta or reverse would certainly be possible even with the props at min. However the effects on control of the aircraft is the significant issue with huge increases in drag, asymmetry and loss of lift contributing to a potential loss of control.

Remember that the propeller blade can be on the low (fine) pitch stops even with the prop lever at min. If the power setting is low then as the airspeed reduces the propeller blade angle will fine off(attempting to maintain a constant Np) until it reaches the low pitch stops resulting in a Np reduction. In this case a selection of the prop lever to max will have no effect on blade angle or Np (unless power is applied). It simply removes the interlock to allow selection of beta on landing.

I have to agree again with Sheep, if the aircraft flight manual dictates a procedure its a good chance its in there for a reason.

Another great post to get every one thinking


:ok:

[GW_04]

Hi splatman
that was nicely put there.

If I may add to the beta/reverse mode.

To explain a little further on the interlock mechanism you mention, it is more a design thing than a safty thing as such.
The primary governer will continue to controll prop rpm at whatever speed the prop levers are set to, only up to a certain point where power (Ng) setting or airspeed will no longer maintain the set rpm. This is where the primary blade angle (beta nuts/fine pitch stop) becomes critical. ie the prop reaches full fine.

It vary's between aircraft depending on there approach speed prop type/rpm etc..
Only once the prop reaches the fine stop, then the prop rpm falls below the governed setting, that the spool opens up to bypass oil to the beta valve. This is the interlock mechanism you talk of splatman.
Once in beta mode (separate governer) the power lever then controlls blade angle directly.
This is why if you have to low an rpm setting in a PT6 on approach or landing, the rpm may not drop sufficently below governed range for the spool to bypass to the beta valve. There fore rendering it locked so to speak.

As a note...the high idle, or flight idle on the Ng is a fairly critical setting too in all this as a too higher setting here will cause the prop to stay in the goverened range also.
Most a/c manufactures have these settings fairly well laid out in there maintainance manuals. Some do not!
Believe me, after helping engineers rig some types, it can be quite a tricky process getting them right. Sometimes only the flat of a nut to make all the difference.
Bit of a genius who designed it all I reckon.
Hope this helps some...;)

Cheers G

[Spinnerhead]

Excellent GW_04,

Now I know why you have to slow down before you can select beta mode whilst airbourne for that faster descent!
And why you can still select beta without full fine, however it will be at a slower forward speed.

[triadic]

Props up on final when an increase in rpm does not result is usually a good rule. Nothing worse that hearing the revs increase on final.... does not do the engine much good either and it does not have to happen!

[splatman]

GW_04

A very nice engineering explanation of the workings of a basic PT6 beta system, however it appears you are implying that once the blade angle is on the low pitch stops the interlock is removed and beta may be selected and controlled by the power levers.

I havnt looked at a PT6 for some time and deal with PW120/123's now. But ,my memory tells me the system has a little more too it than what you have indicated. Your explanation certainly details the select and follow of the beta system however the interlock I refer to is a mechanical interlock that is related to the propeller lever position.

Early DHC6 aircraft had a props reset warning light fitted (large red flashing unit) to warn the crew that the props needed to be full fine prior to selecting Beta. As the mod status changed then so did the need for large red flashing warning lights, (to a small caution light).

If you hava access to a DHC6-300, when on the ground with the engines running and the power levers at flight idle, set the props to min. I think we both agree that the blades will be on the low pitch stops and it will be out of the governing range. Then try and select beta. You wont be able to, unless the props are set to max, that is the interlock I refered to.

That interlock is different to the locking up, so to speak that you talk of ( or at least I have interpreted your intended meaning) which is similar to that is experienced with the engines shut down and you try and select beta. The whole system locks up and forcing the power levers aft of flight idle may well result in damage to the mechanical components of the beta system.

Excellent post GW_04, certainly gets every one thinking and very worthwhile for some that find the beta system a little of a mystery.


:ok: Great Stuff

[betabackup]

I agree with BW and Splatman.
The interlock is to stop the selection of the beta/ reverse range in flight as the interlock system only allows the power levers to come back to the idle stop untill one or both props are reset past 95%.
Where as the beta backup system prevents the blades being driven into reverse pitch in the event of a failure of the hydraulic low pitch stop.

In the Aerostar flight manual full fine is selected after landing.

In some garrett engined aircraft full fine needs to be selected so as the aircraft 1. Has power available 2.so as it can land as designed to without running on due to the underspeed govenor kicking in at flight idle and extending the landing run.

Each aircraft/ manufacturer have there own way of doing things and usually there is a good reason behind this.


Just my two cents worth........................

[Reverseflowkeroburna]

I'd have to say GW and splatman are pretty much on the money!

The B200 has an annunciator, "Reverse Not Ready" which comes on when the gear is down and the prop levers are NOT at max. Note I said levers and not props! I'm no engineer, but to me this pretty much means "Reverse Not Ready!"

The same A/C also warns via a placard of mechanism damage if power levers are moved aft of flt. idle with the engines not running! I can only guess at some sort of interlock as per previous posts!!!???:ok:

As for pistons, I prefer final at a speed where the props are already at the fine pitch also.

SOP's have often dictated otherwise though.......with one operator calling for levers to fine once on the deck, and another specifying full fine at the IAF / 5nm for straight-ins / downwind for visual ccts. Their reasoning being that your full attention was available to fly the aircraft/approach!!!

When in doubt......RTFB!!!



Cheers all;)