Pitch controls altitude. Power controls airspeed?

[Capt Claret]

AOTW,

Why would you do both? If you just want to speed up, why don't you just lower the nose?

[Arm out the window]

Gunna have to get a lawyer in to vet my wording here by the looks.

How about instead of saying that power or attitude control airspeed, as one's preference may be, we go with something like 'Airspeed changes in level flight are made by changing power and adjusting attitude accordingly to maintain constant altitude.'

Far too dry but; maybe 'If I want to go faster I increase the power but then I straight away have to lower the nose a bit or else I climb.'

Or, 'Notwithstanding the aforementioned attitudinal or power adjustments, any changes in velocity will be instigated and accompanied by appropriate and fitting changes to the settings extant in attitude (being the visual relationship between the position of the horizon, to wit the perceived joining of sky and/or ground and sea, or the position where such joining may be reasonably assumed to be in the absence of a clear line of demarcation, and such parts of the aircraft in question in the pilot's forward line of sight as are necessary to establish said relationship) and power (that is, the setting of thrust, torque, pressure ratio or other accepted measure of output from an aircraft's powerplant or powerplants) which will be made in such a way as to complement one another and therefore allow the maintenance of an unvarying reading on the face of an instrument fitted to said aircraft for the purpose of measuring altitude.'

Yeah, that's better - sounds just like the CAOs now!

[Sunfish]

If it was a regulation it would look like this:

278.1 A pilot shall not control speed by varying pitch attitude and flight path by varying power.

This is an offence of strict liability.

278.2 Regulation 278.1 does not apply to:

a) Balloons, or;

b) Aircraft with a gross weight of less than 5,700kg, when the pilot in command is:

1. The holder of a valid student pilots licence,or;

2. The holder of a valid Private pilots licence, or;

3. The holder of a valid commercial pilots licence, and the said licence holder does not posses a valid ATPL .

Translation: You do it your way, I'll do it like I was taught.

[v1rotate]

I was taught to use Power to control ROD and Pitch to control airspeed when I was first getting my instrument rating in a PA28. Works in a light aircraft but don't even think of doing it in a 20 tonne F27.

Did anyone get taught to use the rudders to maintain the localiser on the ILS. I always thought that was the worst technique to use. I don't even use my rudders anymore except on the runway during take-off and at the flare/roundout to maintain the aircraft straight.

[Super Cecil]

It's easier just to land the thing, older style steeper approach works for me.
If you treat any powerplant with the respect it deserves you don't bang the throttle on, recip, radial or turboprop.

[Lefthanded_Rock_Thrower]

Mamakim,

What type of aircraft are you talking about flying, light twins or Complex jets ?.

They are very different creatures.

[Mamakim]

I'm talking about small planes mainly.

But I'm also interested to hear about the big jets as well.

I'm tending to lean towards those that say its a combination of both rather than just one or the other. I.e -> I'm not taking the black/white approach......but more the grey (the combination!)

Thanks to all the people that have responded thus far.....seems like there are a lot of different opinions out there.


MK

[Zhaadum]

POWER CONTROLS AIRSPEED as PRIMARY EFFECT.

ATTITUDE (pitch) CONTROLS APPROACH PATH as PRIMARY EFFECT.

Plain and simple.

Today I was flying with a student in a light twin who had some previous twin training and was having BIG problems with circuits prior to his endorsement check flight. He was way LOW and FAST on early to mid final. I asked him how the approach was and he said LOW. So I said fix it. He ADDED POWER (wrong!) and we did not change flight path, the runway still appeared flat and we just speeded up still heading for a house prior to the airport boundary. (Increase of speed does produce pitch up tendancy due lift increase but it is a secondary effect that takes much longer to occur, and now you are more stuffed as you are closer, faster and still on an unstable approach. You should be slowing down towards your Vref anyway, not speeding up!)

I then told him on the next circuit to raise the nose for fixing the approach path and what do you know? We stopped decending, the runway picture lengthened to a normal appearance and the bloody speed (as a secondary effect) ceased being a problem.

We then proceeded to conduct several more circuits using POWER for SPEED and ATTITUDE for PATH (don't forget to trim each time speed changes) and this guy went from zero to hero! Couldn't land to save his life at first, then at the end perfect touchdowns on centreline on mains just after aim point in x-wind and a couple assymetric too.

Couldn't be simpler really.

Cheers!

[Arm out the window]

Yes mate, you refer to what I regard as the correct finals technique - elevator for aim point, power for airspeed. If low, temporarily shift the aim point further up the runway until approaching the right glide path, using power to maintain the correct speed, then reselect the numbers as the aim point.
Slightly different story round base though - no particular aim point, it's more an attitude for airspeed and see how you're going for height, add or subtract power depending on what height you should be at at a particular position and adjust the attitude to maintain the airspeed.
Also in the climb, you maintain airspeed with attitude. It's not as black and white as you say, it's a combination of techniques appropriate to what you're doing.
Having said that, the technique you describe above works very well for finals.

[Lefthanded_Rock_Thrower]

Zhad,

Using the technique you suggest, try doing an ILS or an constant profile NDB, I feel that what Arm out the Window is quite correct.

Also try being high in finals and use your technique ( especially in PA31 with 128 kt VLO ).

The beauty of the Attitude = Airspeed, Power ( flap and gear ) = Performance, it is a stable configuration.

From my experience in piston twin ( mainly PA31, C402, B58, C340, C310 ), an ILS for example i use the follwing for a C310/B58, it works a treat, it is an established approach, i.e. if i was to be distracted during my approach i would be plus or minus 100 ft and 5 kts of where i should be.

Assume, the ILS is 15nm long, you join from 3700 ft ( eg YBCS):

6nm to 1000ft descent to 3700 ft by 20nm CS, by 3700 feet 18-20 inches at 2400 rpm ( 18 light, 20 heavy ).

from 20nm to 18nm allow the aircraft to slow to about 150knots by maintaining 3700, then select APP Flap.

Airspeed should now be about 130 kts, at about half scale glide slope select Gear Down ( go down ), airspeed 120-130, ROD established ( adjust attitude / trim to suite ).

To maintain glideslope, your required ROD will be Ground Speed (GS) times 5 ( look at the trusty Garmin 100 ), check on VSI.

If you are not making your required ROD, adjust power 1 inch at a time, with about 20 seconds between adjustments to allow the VSI to catch up ( you may need to make small adjustments to the attitude to maintain required IAS ).

This is how i fly and this makes flying a approach in IMC very simple, it also is a very simple method of flying a visual cct.

I have not flown a big turbine or jet, i guess theres a reason they call them speed levers in a jet.

[Capt Claret]

Lefthanded_Rock_Thrower

I'm with Zhaadum. I've used both philosophies. I've tought both philosophies.

The premise that power primarily controls speed and pitch primarily controls does not change with flight regime and works with every powered aircraft I've flown from C152 to BAe146, and no doubt it works for B747 and A380 too.

Constant profile NDB or ILS, even the 15ILS or 33 LOC at Cairns, no problem - too fast, reduce thrust/power, as aircraft slows adjust pitch to keep aim point. Too low, raise nose to adjust profile and increase thrust/power to maintain speed.

Simple.

[Lefthanded_Rock_Thrower]

So how do you adjust aim point in IMC ?.

[Capt W E Johns]

You adjust aimpoint when IMC by changing your approach profile, just like you do when VMC. Your question, I suspect, is really 'how do you know where your aimpoint is when IMC'.

[Lefthanded_Rock_Thrower]

Capt Johns, Yes, exactly.

For the 30 year old aircraft that I fly, they are fitted with very ordinary Artifical Horizons ( certainly not a precise piece of equipment ), compared to perhaps a inclinometer / Angle of Attack Indicator in a big/newer machine.

The performance equipment, VSI and ASI that i use (of course there are delays in these instruments), but are relatively accurate tools to use compared to the AH, your thoughts ?.

[Capt W E Johns]

Yes, entirely agree with you LHRT - some AH's / AI's are not accurate enough to allow for very delicate setting of a powerful flight parameter, i.e pitch.

Also, in a lighty the attitude is much more prone to variances around than on heavy/fast aircraft.

For these reasons, when teaching ILS approaches I like to suggest using power to control rate of descent - I think trying to set an attitude to control ROD on an instrument approach is not very practical or accurate in my a/c types. I believe the same applies for most descent regimes, even visually. But that doesn't mean it's impossible or incorrect!

By setting an attitude for an airspeed, you're left with power to control ROD/glidepath. Not on glidepath? Adjust power by a very measurable amount (a few percent/psi/inches as your steed dictates), and wait for the results. Rinse and repeat! Sure, speed will now be your major variable, but for an ILS I'd rather accept a speed inaccuracy than an altitude error.

Anyway it's really a matter of semantics... connect both gloves with a piece of string running around the back of your neck, and you'll normally get it right.

[psycho joe]

By setting an attitude for an airspeed, you're left with power to control ROD/glidepath.

With regard to an ILS, angle of descent is fixed therefore rate of descent is dependant on airspeed but not controlled by airspeed. By setting POWER for airspeed and adjusting ATTITUDE for ROD = PERFORMANCE.

Sure, speed will now be your major variable, but for an ILS I'd rather accept a speed inaccuracy than an altitude error.

Why would you accept either??

[Chimbu chuckles]

LRT on a CANPA your adjust your path to the 'aim' point (a alt/DME dist) with reference to a profile. Therefore if you're off profile you change attitude to adjust your ROD (flight path) and use thrust to control your IAS.

If you are high what will effect change quicker...lowering the nose or reducing power/thrust? You want to effect chage quick because then you need smaller changes and can be more precise.

[Arm out the window]

It seems that on visual finals in a lightie, or on the ILS, the attitude for profile and power for speed works pretty well because you have a direct visual representation of 'how you're going' with respect to the desired glidepath.

However, in response to Psycho Joe, it's groundspeed that's important for angle of descent, not airspeed.
With fluctuating airspeed, for example (as Capt W.E. Johns says) in a lightie you are bouncing around; and so chasing the glideslope with attitude can be a pain in the arse, much more so than in something that's got a bit of penetration (oo-er matron!), therefore you may be better off selecting an attitude to stick around your desired airspeed as best you can, and make adjustments to power as you see a trend developing to hopefully peg the power that's going to give you an appropriate ROD for the average wind component down most of finals.

Then of course you'll get the hills and/or sea breeze stuffing it all up anyhow!

[Lefthanded_Rock_Thrower]

Chimbu,

In the lighties i fly, if you where to push forward as you suggest you speed up and go from the back of the drag curve to the front.

Going from the back of the drag curve to the front makes the profile problem worse, i.e less pwr required therfore more excess power, or in this case less deficiency of power ( less ROD for a higher ground speed ).

Remember the Forward and Reverse Command thing:

In the high end of the Drag Curve you pull back, a decrease in airspeed cause more excess power ( more climb / less descent ) - *Pull back, go up*.

In the back half of the drag curve, you pull back, the airspeed decreases and you have less excess power ( Less climb / more descent )- *Pull back, go down*.

With the big shiny aeroplanes that don't leak oil that you fly, what do you call them again,,,,,,, ummm,,,,thats right " Airliners", your drag curve is a lot larger in range ( for example 120- 500 kts ), therefore less steep, smaller changes in Excess power for the same airspeed change.

Then theres the "Hot stuff out the back is less efficient at low airspeeds compared to our propellors".