Throttle use on approach

[Speedbird252]

Evening to you all.

Ive just watched one of those "in the cockpit" videos of a 757-200 from Manchester to Dalaman. Im curious about one aspect and its not a 752 thing only im sure.....

The approach turn inbound was at 8DME and the flaps and gear taken in the turn for a fully visual man land at Dalaman, Turkey.

All the way down the approach the P1 made constant adjustments to the thrust levers, I presume to control the descent rate. In PA28 or a 152 etc, the response to this action is immediate and as a result gives precise and responsive control over the entire approach. My question is that how effective is this method when flying a fully manual approach in a Jet? I imagined that the spool up/down time would be such that the ability to control the descent rate on approach would be rather to little, too late!?

Are these Power Plants twitchy enough to do this!?!?

You guys and gals make it look so easy........

Kind Regards to you all..

[nohat]

The thrust levers are used to control speed in a jet.

We set the body angle at 2.5 degs nose up in the landing config. Then select around 1.2 EPR as a rough power setting at normal landing wt.

Small adjustments have to be made, but thats about the gist of it.

We don't use the rudders to stay on the loc in a swept wing jet either as it causes more problems than it solves. (as a generalisation) I read a post by someone who was finding out the hard way.

Small A/C flying, has significant differences in technique when compared to large swept wing A/C.

All in all it's something you learn very quickly.

Fly Safe.


Please God grant this Forum a spell check!!


[This message has been edited by nohat (edited 29 April 2001).]

[FJJP]

There's a thing called 'slam check' which is done on air tests. This is where you literally slam the throttle from the idle position to full power, at the same time starting a stopwatch. This is to check that the engine fuel control system is working as it should. Times vary - the older design of engines can take as long as 10-12 seconds to reach full power from idle, the more modern engines a lot less. The acceleration is not linear - that is, to begin with the engine responds very slowly. However, as the %rpm increases beyong a certain figure, say 80% (it varies from engine type to engine type) the acceleration becomes very rapid indeed.

An approach is always flown with flaps and gear down, and to overcome the drag, the engines are set at a fairly high rpm. This means that adjustments in power are felt quite quickly. The engine response is not, therefore the problem.

The problem is with the inertia. A big aircraft is slow to respond to small power changes, but as Nohat says, it is something you learn about in training and adapt to very quickly.

Hope the simple explanation helps clarify - it's not magic, it's experience!

[tailscrape]

Yes, I agree with the above posts. Typically, it will take about 6 to 8 seconds for an RB211 to spool up from idle to full power....or something like that.

In our SOP,s we have to be fully stabilised in the chosen configuration at the VERY LATEST 500 feet above ground.

That means: Flap and gear etc. AND thrust selected and in the range of 1.2 EPR, so in case of wind shear or such, you can click the go around switch and receive pretty much instantaneous power to climb away with.

As someone once said to me: Fully stabilised is not 4 whites, no power, nose down and good speed. It is just as equally not 2 reds and 2 whites, good speed and power off......

But it is not exactly rocket science .

[CaptainSquelch]

So you're a rocket scientist .... that don't impress me much :)

Sq

[AffirmBrest]

Interesting that you guys use EPR as a thrust ref when manually flying (are you all on the 757?).

Airbus main parameter is EPR (on the v2500s anyway), but I find it a lot easier to use N1 for power setting when using manual thrust - it's probably just a personal thing but I find that a larger change in the numbers for the same thrust change makes it easier to assess the accuracy of my thr setting. Also, is it me or does N1 respond to a Thrust lever position change quicker than EPR? Feedback welcome!

45% N1 for finals fully configured in a A320, give or take a bit for weight.

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...proceeding below Decision Height with CAUTION...

[CHICKENTRAINER]

Speedbird,

When you fly your PA28 or C152 I would argue that you should use POWER (throttle) for airspeed control and ATTITUDE (pitch) for aim point. The only time this won't work is when you are at full throttle or idle power and then you must use the secondary effect of pitch attitude to control the airspeed.

If you think about the old wives tale of attitude for airspeed and powere for rate of descent, then to commence the take off roll, you should line up on the runway and then lower the nose to accelerate.

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ChickenTrainer, on PDL

[nohat]

AB.

In answer to your questions, I am dual rated and fly 767-200/300 and 757's. You are correct in that EPR is a rough way to set power when fine adjustments need to be made.

I only use 1.2 EPR as a starting point and then bring N1 into the scan for fine tuning.

As a matter of interest the N1 setting is about the same on both 767/757 on approach.
That is around 60-65% N1 on both GE-C2 and RB211 engines.

Makes the whole thing a lot easier.

[nohat]

Chickentrainer, I have spent many many hours "bashing" the circuit with my students before I became a Boeing driver.

You use power to control ROD and pitch to control IAS in the landing config in a light A/C.

I have no idea if you are an instructor or if you have ever been one, but I suspect not.

Unless aerodynamics have changed since I used to be an instructor, I think you will find that PPL's are still trained this way.

I have not instructed for some while now and techniques could have changed.

Maybe a current instructor would like to step in and tell me IF this is so.

Duh, still no spell check!!!!!

[This message has been edited by nohat (edited 30 April 2001).]

[This message has been edited by nohat (edited 30 April 2001).]

[Tor]

Chickentrainer

If you are too high on an approach, try this: Dive the nose to correct your altitude. Then slam the throttles back to correct the building speed. What happens? At the end you'll find that you may end up at the correct altitude but too fast and unable to slow down. This is what you suggests to do?

The try the following instead: Slam the throttles back and only adjust the nose to maintain the correct speed. You'll find that you'll get a much steeper decend.

It's been tested :)

[low n' slow]

I might not be able to flare correctly (see my previous posts!), but I've not had any problems with my approaches. I do it like this: downwind, I get established at 90 IAS with flaps 10.
base, reduce speed to 80 and set flaps 20. This is where the speed reduction process starts. I pull back on the throttle quite significantly at the same time as i raise the nose to bleed off the airspeed. When I have 80 IAS, I let the nose drop to the correct glideslope and increase throttle so as to maintain 80. The same thing goes for finals, where I reduce power and wait for airspeed to bleed off to 70 and then let the nose drop to glideslope.
I find that on a good approach, I should be able to correct the variables with both pitch and power. If not, I'm either too high or too low. All this is based on my training on the C172 so I'm not shure of how it works for the big birds...
cheers

[glider insider]

Chickenman....think of your statement if flying a glider on approach...a more simple aircraft. consider your airbrake to be your engine..

( i.e full airbrake is power at idle)....

if undershooting the standard procedure is to close a/b's, hence reducing RoD and extend the approach...
in your version of flying pull back on stick to reduce RoD and you get into the nasty situation if unexperienced of stalling on the approach....not a good move in any aircraft type

perhaps you should fly a bit more...even if it is just in a glider...the principles are roughly the same.....

[Tor]

Excellent point, glider insider, never though about explaining it that way.

low n' slow, if you're going to fly an ILS that way, you'll have some serious problems maintaining the glideslope.

[fly4fud]

Flying the fan driven Sunday craft or the mini 4 holer during the week, I just fly the thing and don't think about what I'm doing...
Guess it's called instinctive piloting :)

Joke apart, setting about 62% N1 (according weight and ATC) on the ARJ85/100 seem to do the trick. Then just extend/lower the bits, and there you are, a grease...
(P.S. the ARJ is of course THE most forgiving aircraft in the world ;) )

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... cut my wings and I'll die ...

[CHICKENTRAINER]

nohat

Can you please explain to me why in a jet you use thrust levers to control speed but in a light aircraft you use pitch attitude?

You give me a precis of your instructional background and I'll give you one of mine.

Tor

If I was too high on approach, commensurate with lowering the nose to regain the desired approach path, I'd reduce power, because I know the speed will increase as a secondary effect of lowering the nose.

If I was too low, I'd raise the nose and increase the power.

I don't know about you, but I'd never slam the throttles either way. If my attitude/pitch corrections didn't look like working, I'd go around and try again.

Glider Insider

I don't think the comparrison is correct. With powered flight, the aim is not to fly a glide approach but a powered approach.

I bet none of the powered flyers when they commence descent from S&L in the circiut reduce power first to start descent. I;ll bet they lower the nose perhaps simultaneously reducing power to control the speed.

For some obscure reason, the old wives tale of power for airspeed and pitch for RoD, (but only in a lightie!) has krept in over the years.

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ChickenTrainer, on PDL

[low n' slow]

Thanx Tor!
I haven't started with my IR yet so I guess I'll have to get rid of that nasty habbit. Works for VFR though!
cheers

[Flap 5]

Tor,

Not sure I would agree with you. Any aircraft has a best rate of climb speed. That is the speed at which you will also descend at your slowest rate. If you accelerate to a much higher speed you will create more drag and will descend much faster.

Hence on a jet the speedbrake is much more effective at high speed than at low speed. It is also well known on a jet that they do not go down and slow down at the same time very well at all. So if you want to go down you increase speed and only slow down when you level off.

[Tor]

<font face="Verdana, Arial, Helvetica" size="2">Chickentrainer:

If my attitude/pitch corrections didn't look like working, I'd go around and try again.</font>

So you go around a lot? ( :))

Seriously, you should try setting up for a very steep approach, it makes good practice.

It's basic aerodynamics. You would want the most induced drag if you want to get down quickly. The best way of getting that is not to lower the nose and control RoD with power.

On another node, don't you remember what makes an aircraft decend? Deficit of thrust!

Who says it only goes for light aircrafts?

<font face="Verdana, Arial, Helvetica" size="2">Flap 5:

If you accelerate to a much higher speed you will create more drag and will descend much faster.</font>

Yes but were talking about approach and not decend. Try bleeding of the excess speed in the flare and you would almost certainly make an overrun

[This message has been edited by Tor (edited 01 May 2001).]

[kabz]

One thing chicken missed is that you should always try to be within gliding range anyway.

As far as his setting up a descent goes, he is dead wrong about dropping the nose and reducing power to slow down. Actually, even in a 172, you have to drop power, typically to 1500ish RPM, ***wait for it to slow down*** ***in level flight***, then allow the nose to drop to maintain 75, 80 kts in the glide.

At this point, pitch controls airspeed, and you can add or reduce power to change your landing aim point.

Also, contrary to what chicken says, to come down faster, you can raise the nose a little, to slow down and use a less efficient glide. I believe that 75 kts is best glide for distance in a 172, and 65 kts is best for time, within reason you can use the slower speed to come down flatter but steeper, though you may need to add power near the flare to land smoothly...

[Pielander]

I think using power to control RoD and pitch to control speed in a light a/c must have something to do with response times. Think about it:

Pitch responds quickly to stick input

Altitude & airspeed both respond quickly to pitch

Alt & airspeed respond more slowly to power setting, but:

Airspeed can drift to an unacceptable (esp. low) value very quickly, so:

Control airspeed with pitch (quick response) and altitude with power (it can wait), otherwise, you end up in the familiar situation of being in the right place at the wrong speed.

I would have thought jets would have had a somewhat more sluggish pitch response and also a more sluggish response in altitude in response to pitch, due to their inertia, hence the reversal of logic.

Out of interest, autopilots control alt with pitch and speed with power, but they also have feedback from power =&gt; pitch and vice versa, so they respond with both at the same time, just like an instinctive pilot.

Pie.

[Tor]

The DC-10 I flew at my MCC responded very well to thrust changes and there was no problems controlling the RoD with thrust and speed with pitch.

[Flap 5]

Tor,

It still applies on the approach. Speedbrake is less effective, so you use the gear and more flap. But again speed against drag works well.

From your posts you appear to be just starting out on jet aircraft. They are a little different to your average Cessna so be prepared to learn (you appear to be quite set in your opinion).

[Tor]

I really don't understand what you are saying. Are you suggesting that it's a good idea to increase speed if you are, say, one dot high on the glideslope?

If that's what you're saying I am quite set in my opinion as that goes the opposite way of everything I was thaught (such as stabilized approach concept).

[This message has been edited by Tor (edited 02 May 2001).]

[Flanker]

Tor
If you are say one dot high on the glide slope you would correct by gently easing the nose attitude down a little and correcting the associated increase in speed by reducing thrust.Keeping the speed correct by thrust lever movement.
It's harder to think about than to do.

[Tor]

I would do it the opposite way. Decrease thrust to get a higher RoD and then let the nose drop to keep the speed. Why would you let the speed increase before taking action, Flanker?

I wouldn't let the speed increase to create more drag as Flap 5 suggests either.

[This message has been edited by Tor (edited 02 May 2001).]

[Skye Pilot]

May I suggest that the idea of pitch attitude controlling speed and power controlling R of D in light a/c is due to the fact that it is an easier concept for a 'student' to grasp, as they will not need to make any secondary adjustments for a properly trimmed a/c. However it is a fairly simplistic method of flying, and once the student becomes competent a coordinated combination of the two methods allow for smooth and accurate flying.

[Flanker]

Tor
Thats the point.If all you do is reduce thrust while keeping the same attitude, the ROD will not increase- the speed will decrease.

To answer your other question the speed does not increase, because you coordinate the movements together, rather than let the speed build then correct it.

Works for me!

[Tor]

<font face="Verdana, Arial, Helvetica" size="2">Flanker

If all you do is reduce thrust while keeping the same attitude, the ROD will not increase- the speed will decrease.</font>

Not if the aircraft is trimmed. You should almost be able to fly hands off if trimmed correctly.
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Edited:
Re-read your post. How do you fly an ILS in level flight http://www.pprune.org/ubb/NonCGI/confused.gif?

[This message has been edited by Tor (edited 02 May 2001).]

[Flanker]

HELP! John Farley or someone.
Looks like I'd better give training a miss.

Tor - You do whatever you fancy. http://www.pprune.org/ubb/NonCGI/tongue.gif

[Flap 5]

Indeed Tor how do you fly an ILS in level flight? Because if you are already one dot high and you level off to slow down, what happens?

Therefore stuff the nose down, get the thrust off and add some drag, or you will be going around. Simple really.

[Tor]

Flap 5, why would you slow down or level off? (I think it was Flanker that wanted to level off).

I said, reduce thrust and let the nose drop to maintain the trimmed speed, not level off and reduce speed.

But to answer your question if you level off and slow down you will stall eventually, a fast way to get down indeed, but probably not opportune :rolleyes:

[This message has been edited by Tor (edited 02 May 2001).]

[Burger Thing]

Hi ,

since there is a bit confusion here, I pull out my good-old book "Fly the wing" - by Jim Webb:

...Airflow around a wing (in a jet aircraft) varies only when the forward speed of the airplane varies. A jet wing is just a board - a lift surface; it goes where you point it, and its speed varies according to the power or thrust applied to it.

The difference in lift characteristics between prop and jet aircraft with and without power requires a diffrent technique in handling approaches. In a prop aircraft you may safely use the POWER for RATE OF DESCENT, but in a jet, you really fly the wing.

For example, if you are flying a prop airplane and getting a little low, you simply ease on a little power. Immediately, AS THE ENGINES AND PROPS INCREASE POWER, THE ADDITIONAL AIRFLOW AROUND THE WINGS GENERATES MORE LIFT. WITH MORE LIFT, THE AIRCRAFT WILL REDUCE ITS RATE OF DESCENT AND STRETCH OUT THE APPROACH TO REACH THE RUNWAY AND THE TOUCHDOWN POINT. Since this power application is usually slight, and increase in lift is also a change in angle of attack, which also produces more drag, the actual speed of the aircraft will only vary a knot or two in forward speed, and very little if any elevator control is necessary.

But this isn't the way in a jet because of its lack of propeller slipstream. When a jet appears to be low, the nose should be raised with elevator control to create a higher angle of attack and increase lift to establish the new desired approach path. At the same time throttles should be advanced to provide the additional thrust needed to counteract the addad drag resulting from the increased angle of attack and to maintain the desired approach speed.

In other words, without props to generate additional airflow, the only way to quickly generate additional lift to change the glide path is to INCREASE THE ANGLE OF ATTACK OF THE WING....

... Hope that helps !

Tor, if you start your line training in a jet and fly an approach controlling the AC in a way you described before, the Training captain will be very busy during the briefing after the flight :)

As soon as you will have a training or 'hands on' you will understand this concept, and after a while it wil become second nature.

[Tor]

This is really getting to be quibbling.

I've never heard of Jim Webb. But that's Mr Webb's opinions - good for him. I'll bet I could find another book that says the opposite.

The version I've heard has nothing to do with slipstream or angle of attack.

But as I said this has gradually more becommen a battle of words. Most would probably agree that it's a combination of diligent use of both throttle and yoke.

What seperates us here is what action should you do first - correct pitch or thrust? And I'd say thrust (since altitude is also energy, and you want to get rid of it if your high).

By the way you can fly a plane without the elevator if trimmed for the correct speed, but can you fly it with stuck throttles? ;-)

[kennedy]

There are two methods to conduct an approach, pretty much everyone agrees with that at least.

I was originally taught the Power for ROD and pitch for airspeed method, which is simple to learn and works well in a/c upto Seneca size but not for anything bigger as momentum and inertia start to interfere.

I was then taught the 2nd method of controlling speed with power and maintaining glideslope with the pitch attitude, which not only works for light twins upwards, this method also works for light singles!

When first introduced to this new method by a couple of experienced CFI's and CP's I resisted learning the new technique, as I still flying C172/182's PA 28 etc at the time.

I am now glad that I know that 2nd technique as I use it daily, can't use the power/ROD method in an airliner.

However, remember it is horses for courses, as you might only want to be flying bugsmashers and the power/ROD method is fine. But always have an open mind for advice for all types of pilots, your instructor might not know everything. I certainly don't!

[Flanker]

Tor

Go on then.Find a book that backs your 'technique' as applied to jet transports.
Is there anyone else who actually operates this class of aircraft who would agree with Tor?
By the way you can keep a constant attitude in the descent as well as in level flight!

I would have much more patience with you if you actually had some time on the class of aircraft we're talking about.I get the impression you would be a source of deep joy to a training department.

'Fly the Wing' is on my shelf too, the author,Jim Webb was an Eastern pilot with over 35000 hrs.But hey what does he know compared to you?

[Flap 5]

Flanker,

I reckon this guy Tor has to be a wind up. If not and he gets to fly jets I would love to be a fly on his cockpit wall with his training captain, I certainly wouldn't want to be a passenger!

[Tor]

Guys, take it easy.

Flanker I re-read your post a third time. I am sorry I mis-read attitude as altitude. Why would you keep the same attitude? You would also have to re-trim or excert a back pressure on the yoke - again why? That's is not what I'm suggesting and you know that!!

I like kennedy's reply "But always have an open mind for advice for all types of pilots, your instructor might not know everything. I certainly don't!".

You, Flanker and Flap 5, seems not to be very open minded. You are very set that only you are correct and nobody else. I havn't said you're wrong, I just said that this methode works very well for me, and subsequently defended my standpoint.

As said I have no jet-experience besides from 20 hrs in a DC-10 sim. However, if you must ask it went very well - thank you :)

I really think that you guys are very low in you arguments when all you can come up with is personal attacks. I might be tempted to say go back to you FS98 or whatever... But I won't http://www.pprune.org/ubb/NonCGI/tongue.gif

[This message has been edited by Tor (edited 03 May 2001).]

[Flanker]

Tor
Jeez, sensitive or what!
People here are trying to teach you something,not argue with you!
The point is that if Jim Webb was your instructor on your first jet job,I get the strong impression you would be arguing with him too.
This would be good experience while looking for your second jet job shortly afterwards.
Learn the easy way.

[Burger Thing]

Hey Guys, keep it low....

The explanation out of Jim Webbs is very basic aerodymacis and shouldn't be very difficult to understand. I don't want to have an emotional discussion here, it is just my personal advice to you: take your time and think about the effect of slipstream, inertia, angle of attack.

I think it is just natural, that when you have very little of experience, then whatever you hear from an instructor, it is written in gold. But instructors are humans and like every human beings they do mistakes, and in my opinion your instructor told you something wrong. You will see it, when you will have some more experience.

But please, change your attitude a bit and be a bit more open minded to the pilots, with have a bit more experience than you, otherwise you really will have some problems later on. I didn't write all this sentences from Jim Webb just because I was bored, I just wanted to help you a bit, for your benefit. And like it was corectly said bevore, Jim Webb had 35000 hrs of experience....

When you fly a jet in IMC in an ILS approach, you really need to fly very precise, especially when coming close to the minimums. If I would raise the nose to correct the airspeed, you would be immediately below/above glideslope.

I don't have any experience on a DC-10, but maybe this partucular aircraft is not the best exapmple, because of the position of ENG Nr.2, which is located well above the height of he CG, which gives you maybe a momentum around the lateral axis.

When you did your sim on the DC-10 sim, you had no previous jet experience, and for sure you were really overwhelmed and in an MCC course different things are required than for example later during a type-rating checkride, or a line-check. Then you have to fly by the numbers and very precise. Your previous methods won't work, I guarantee you that.

But in the meantime just be a bit more open minded to facts, which have been proven right for years and millions of (Jet) Flight-hours. http://www.pprune.org/ubb/NonCGI/tongue.gif

[Denti]

I was taught the throttle for airspeed, pitch (attitude) for altitude/ROD methode in my initial training on powered aircraft. Perhaps because it was a training which had the goal to make you good in flying jets. It was quite a change for me because i started flying on gliders. But it worked very well and it's the methode i fly my 737 nowadays.
And in the 737 you can control ROD with the throttle (pitch-up/down moment on throttle-movement), but it's far too slow for a good approach or even level off.

Just my 0.02 EUR, Denti

[Tor]

Burger Thing -

As someone suggested, it's not somthing you really think about - you just do it. And no matter how it's done it's an interaction between both the thrust lever and the yoke.

As I wrote it's just a question of which of them you'll grab first to make the correction.

This has becommen more a battle of words.

[John Farley]

Hi Guys

A couple of pages back I was surprised to find my name. Don’t know why Flanker picked on me (as I’m a MiG-29 not Su-27 man myself)

I don’t believe either side of this eternal argument will ever convince the other they are wrong.

Two food for thought facts:

1 All fixed wing aircraft that have an autoland clearance are designed to control speed with power and glide path with attitude. That includes the Varsity used by BLEU for their first fog landings at LHR in the 60’s When I asked the boffins why it worked that way they said “we tried both techniques and got a more accurate approach with power for speed”

2 Autopilots fly aircraft well.

Now a tale:

When I was a student at CFS my (old) Sgt instructor insisted I patter stick for speed and power for rate of descent. I rebelled and when he threatened to chop me I said “OK Sir (I was a Fg Off but he was the instructor) I accept your technique. Please can I play student and you correct me when I go wrong?” We got on finals (in an early Jet Provost) I got slow but on the correct glide path and at 30 ft over the lead-in lights I said “You have control Sir - please show me how to lower the nose to get the speed back” He slammed the throttle forward and kept the nose where it was. Rebels 1 Oldies 0

But trying to be constructive, surely all fixed wing aircraft can be flown either way and different human pilots make different choices (for the way they think about it in their head) depending on their background and the characteristics of the aircraft type in question. HOWEVER, and yes I am shouting, both schools of thought actually require BOTH throttle and stick to be used and co-ordinated. Which is why both systems work?

(just like Tor said while I was away writing this)

Me? I used to try and mimic autopilots because they flew better than me.

Good here init?

JF

[Burger Thing]

Well... I don't see this as a battle of words. I just wanted to be constructive and help you a bit. The methods I decibed is just simple aerodynamics. For this reason boths methods can't work equivally in a jet. And if you tell me, that you bring up the nose in a jet on an ILS im IMC in order to bleed off the airspeed and then add power to reduce the RoD then it is simply wrong. You would NEVER be able to fly a good, PRECISE approach. In a jet you fly the attitude - especially on approach.

When you have the flaps FULL extended, you need a lot of 'parasite power'. If you raise the nose, the change of required 'induced power' (because of the higher AoA) is not so significant compared to the still unchanged 'parasite power'. The effect is: the rate of descent will change, but not so much the airspeed.

[Checkboard]

Flanker, I thought I might help Tor out a bit :) :

<font face="Verdana, Arial, Helvetica" size="2">For the condition of steady flight with a given airplane, each angle of attack corresponds to a specific airspeed. Each angle of attack produces a specifc value of CL and each value of CL requires a specific value of equivalent airspeed to provide lift equal to weight. Hence, angle of attack is the primary control of airspeed in steady flight. (Page 350)

...it is apparent that power setting is the primary control of altitude in steady flight.

FLYING TECHNIQUE. Since the conditions of steady flight predominate during a majority of all flying, the fundamentals of flying technique are the principles of steady flight:
(1) Angle of attack is the primary control of airspeed.
(2) Power setting is the primary control of altitude, i.e., rate of climb/descent.
With the exception of the transient conditions of flight which occur during maneuvres and acrobatics, the conditions of steady flight will be applicable during such steady flight conditions as cruise, climb. descent, takeoff, approach, landing etc. A clear understanding of these principles will develop good, safe flying techniques applicable to any sort of airplane. (Page 352)</font>
Aerodynamics for Naval Aviators H. H. Hurt, Jr.
Issued by the Office of the Chief of Naval Operations
Aviation Training Division
U.S. Navy

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Tech Log forum moderator

[Flanker]

John.F-picked you for two reasons:

1)You said elsewhere with regard to teaching'There is no such thing as an impotent man, only an incompetent woman'

2)You very kindly gave a friend of mine a lift to/from Ireland in a Ryan? a few years ago ,so you must be a good bloke!

Checkboard

Nice try! but I was specific about jet transports when I raised the book challenge.The Vigilante and the Tomcat barely qualify.Mind you there were rumours of a Herc on a carrier! :)

Tor 'will not let it Lie'(Sorry Vic)and is regrouping and attempting to recruit in the Tech forum this very minute.

[John Farley]

This thread has much to interest/excite/infuriate etc any pilot who thinks about how he or she flies.

As further evidence of why I think the issue will not be resolved in my lifetime (resolved that is in the sense that everybody will start thinking the same way) you might be interested to know that the VAAC Harrier aircraft which is carrying out research for the JSF programme has been set up to allow pilots of either persuasion to fly it “their way” So, in this totally computer controlled aircraft you can choose a mode that lets you use your left hand to control speed OR one where your left hand controls flight path. Now who says computers don’t have their uses!

Yet more evidence that the whole thing is in the pilots head is the super quote produced by Checkboard a couple of posts back (sorry I don’t know how to do the fancy stuff)

Quote

FLYING TECHNIQUE. Since the conditions of steady flight predominate during a majority of all flying, the fundamentals of flying technique are the principles of steady flight:
(1) Angle of attack is the primary control of airspeed.
(2) Power setting is the primary control of altitude, i.e., rate of climb/descent.

End of Quote

Don’t you HONESTLY agree it would have been just as easy (and even correct) to write

(1) Angle of attack is the primary control of lift (after all what do YOU do in the steady state when you want the altimeter to go up a tad - tweak the stick or fiddle with the throttle!!)

(2)Power setting is the primary control of speed

See what I mean?

JF

[Tor]

Thanks for helping me out Checkboard

Flanker, I can clearly see the logic, pitch for speed and thrust for RoD/RoC is only applicable to Cessnas and Tomcats. Of course the Tomcat has a lot of slipstream from it's propellers http://www.pprune.org/ubb/NonCGI/tongue.gif

Regarding Jim Webb's book, I have no idea about his credentials, but there is an interesting article on www.avweb.com (http://www.avweb.com/articles/pelperch/pelp0003.html) by John Deakin who also have thousands of hours - it's called What really counts.

<font face="Verdana, Arial, Helvetica" size="2">Burger Thing

And if you tell me, that you bring up the nose in a jet on an ILS im IMC in order to bleed off the airspeed and then add power to reduce the RoD then it is simply wrong. </font>

That's what I would do assuming that you mean low and fast on the ILS.

<font face="Verdana, Arial, Helvetica" size="2">John Farley

Don’t you HONESTLY agree it would have been just as easy (and even correct) to write

(1) Angle of attack is the primary control of lift (after all what do YOU do in the steady state when you want the altimeter to go up a tad - tweak the stick or fiddle with the throttle!!)

(2)Power setting is the primary control of speed</font>

The reason I believe it's easier the other way around and was I was thaught is, that altitude is energy. If you want up put in some more energy and vice versa.

[John Farley]

Tor

Bingo! If you find it easier that way then that is the best reason there is for doing it (or anything else for that matter)

The last time I flew the USN system (throttle glide path) was in a T45 Goshawk back in 1991 out of Pax River. But I don’t believe techniques or teaching have changed since then. Like all Navy aeroplanes (including RN ones when they had Buccs & F4s etc) it was especially equipped to help the pilot fly a VERY accurate approach to a ship.

As I’m sure you know on the aircraft there is an AOA “indexer” which is used to fly a very accurate AOA and on the ship there is meatball to help you fly a very accurate glide path. The bloke (on the deck) monitoring and assessing your approach (and every one is assessed) can see how well you are flying the ball because he has a shufty scope that lets him track your glidepath, while the aircraft AOA indexer drives a set of lights on the nose leg that shine TOWARDS the ship telling everyone how well you are controlling AOA. What nobody knows is what is going on in the pilot’s head IE which hand he or she is using to control which indicator.

Now of course we know Navy pilots do it the way they are told to.….really? How?
The point is it matters not a jott so long as you control both parameters within the necessary limits by coordinating your controls. And if you are sensible you will do it the way that is easiest for you.

It happens I found it easier “the other way” but so what?

IMHO the trap is to feel you must prove your way is theoretically better.

End of broadcast.

JF

PS It would never do to suggest that if the Navy aviators didn’t do it differently (and of course better) then they would be just the same as Airforce ones eh?

[John Farley]

Tor

Sorry, I forgot to properly reply to your last point.

You remarked that in your head height is energy. Too right its potential energy. In my head speed is energy (kinetic energy)

See - it works for both of us!!!

JF

[Flanker]

JohnF
You have the patience of a saint.I'm a Scot so no chance there.

Tor
The Tomcat doesn't have props but its not a jet transport. Jaguar/Harrier boys may disagree!
How do you get the bold into your messages please?

By the way I'm going to think about the other technique flying later today so I hope I don't say 'I told you so' in the Sun tomorrow!

[Tor]

Flanker -

To the left of the text window where you type your reply there is a link called "UBB Code is ON". Click on it and it say all about how to make italic, bold, quotes etc. It very simple you just type [b] to begin bold and [/b.] to end it (without the dot - had to put it there so you could see it). Replace "b" with "i" for italic and "quote" for quotes.

-----

Anyway, perhaps this topic has been debated enough. John Farley makes very valid points.

Fly safe Flanker :)

[Flanker]

P.S
By the way I have met John Deakin in California and he writes a whole lot better than he talks-he completely ignored me.Very disappointed in him.Very unlike the other people I meet in the US, they are usually superbly friendly.

Does he have a view on the subject we're discussing?

[Tor]

Not directly. It was with regards to Jim Webb's book and your comment that he's got 35.000 hrs. What does that really mean or count for? That's what John Deakin reflect on in his article (not Jim Webb's hours but his own http://www.pprune.org/ubb/NonCGI/tongue.gif). John Deakin's point is it doesn't automaticly make you an expert because you have lots of hours. What should be focused what has he/she been doing etc., what is their reasoning etc.?

The link I made in my previous post is a direct link to the article.

[This message has been edited by Tor (edited 04 May 2001).]

[Burger Thing]

...Ok, one last statement, because finally it is getting a bit tiring, because I think these things are not really too hard too understand.

<font face="Verdana, Arial, Helvetica" size="2">And if you tell me, that you bring up the nose in a jet on an ILS im IMC in order to bleed off the airspeed and then add power to reduce the RoD then it is simply wrong.
--------------------------------------------------------------------------------

That's what I would do assuming that you mean low and fast on the ILS.

</font>

Guess what ? I would do exactly the same. I thing, you really have a lack of understanding here. First you correct the most critical parameter, which is in your scenario the glidepath: too low. So you bring up the nose, then you correct the airspeed.

I just wanted to give you an example, why your theory of power controls pitch, AoA controls airspeed wouldn't work: when you are exactly on glidepath and your speed is too fast.

I don't want to give you via the internet a lesson, how to fly a commercial jet transport. Your training captain will rectify your lack of understanding. :rolleyes: Good luck

[Tor]

So you're saying if you're on the ILS but too fast, you'll just cut a little back on the thrust but do nothing about your AoA (because, ohh thrust controls speed)?

For your information it not my theory. I didn't invent it. Most likely half of pilots use the one and the other half the other. I think you're being pretty arrogant here! (Did you even bother to read Checkboard's post?)

[This message has been edited by Tor (edited 04 May 2001).]

[Tart with a twist]

Power for ROD and attitude for speed is a useful instructional technique especially in a student's early stages, and would be appropriate for some types of approaches.

I was taught a short field technique by an ex Vietnam Cessna Bird Dog pilot, as follows:- In a close downwind, close throttle, maintain nose level attitude and flaps out as speed allows. The aircraft slows, sinks and stabilises at approx 1.1 x Vs. The descent is steeper than usual but not alarmingly so, but is such that there is a clearly defined landing point. Power is added to stretch the glide, until the aiming point is the required touchdown spot. The attitude is still approximately that of cruise. The flare is of course critical, float minimal, impact firm, but incredibly accurate.

My mentor was also a Cessna demo/test/delivery/instructor pilot for many years, and as he showed me, the technique worked for singles up to and including the C208 Caravan.

On a precision approach however, I would contend that a glideslope is best maintained by pitch changes, once you're established on it, and hopefully they'll be so minor that the resulting power changes will be minimal. In other words if I'm half a dot above a glideslope the first thing I'm going to do is pitch down, with a thrust change only if necessary. I feel this is as valid for single engined props as it is for jet transports.

And no, I didn't teach that STOL technique to my students!

Regards - Tart with a twist.

[Speedbird252]

...blimey!! And to think I started all this! Keep it coming guys, You have all taught me a great deal already!!

And John Farley, I fly out of Goodwood......!!

Small world..

[CHICKENTRAINER]

A dissertation (rambling) on fixed wing flight.

by ChickenTrainer.

To fly, a fixed wing aircraft needs energy to provide either, acceleration to, or maintain, a sufficient airspeed that the fixed wing can generate lift. As we all remember from PPL aerodynamics, the required lift can be generated at high angle of attack and low speed, or high speed and low angle of attack, or somewhere in between. Generally fixed wing aircraft gain the acceleration, or maintain the required speed through the air by use of one or more engines, driving a propeller, or perhaps jet engines.

In part, flight can be said to be an exercise in energy management.

At the commencement of the take off, potential energy in the form of fuel (Avgas or Avtur) is converted into heat thence thrust. This thrust, directly controlled by the throttle/power levers/thrust levers causes the aircraft to accelerate down the runway. At an appropriate speed, the nose is pitched up, and the aircraft breaks free of the ground and commences climbing away.

Let's say a pitch attitude of 10o is set and maintained and the power is left as set. The aircraft will accelerate as it climbs away to a speed that uses all the energy the engine/s produce. The thrust energy from the engine will be converted into kinetic energy (speed) and potential energy (altitude). Of course as altitude is gained the thrust energy output of the engine will reduce. If left unchanged, the aircraft will eventually reach a level where there is no excess thrust energy be converted into potential energy (altitude) and the aircraft will level off.

Should the pilot decide to lower the nose at some point, then the flight path will change, almost immediately. As the flight path flattens out, with the lowering of the nose, the energy requirement of the aircraft will change. If we assume the pitch attitude is set to maintain a LEVEL flight path, then more of the thrust energy is now available to go to the speed side of the equation and the aircraft will speed up. Once the aircraft has achieved the desired speed in level flight ( commensurate with the aircraft type) the thrust is re set to maintain the speed and thrust energy equals kinetic energy.

Should decent be required, the pilot has a number of choices. S/he can lower the nose, thus initiating a descent. Effectively travelling down hill, this will reduce the proportion of thrust energy required to maintain speed, so the pilot either accepts the speed increase, that is, potential energy (altitude) plus thrust energy is greater than that required for the speed, so kinetic energy increases, or, the pilot can reduce the thrust energy by an amount equal to the conversion of potential (altitude) energy in excess of that required to maintain speed.

Alternatively, from the steady straight and level state, the pilot could simply reduce the thrust. If the pitch attitude is maintained, this will cause a decrease in speed and thus lift, which in turn will cause the aircraft to descend. BUT, the aircraft is descending because the lift has been reduced as a result of the primary effect of thrust that is speed.

Rambling dissertation ends.

When I commenced my flying career, as an instructor, I was forced to teach this method, as the Chief Instructor and Chief Flying Instructor, both insisted on it, and infact spent a couple of hours in the circuit with me before letting me lose on any students.

It was contrary to the way I was taught, as I was taught the traditional Power for ROD, Attitude for Airspeed. Once I was convinced, it was easy. Far easier than the traditional belief in that the culture of Power for Speed and Attitude for flight path, doesn't change with type. It is instinctive, if low, raise the nose, one knows that if one raises the nose and one was 'on speed' the energy requirements have changes and a commensurate change in power will be required.

The real benefit to Power for Airspeed and Attitude for Flight Path, is that the pilot's thinking doesn't have to change just because s/he is approaching to land.

So, apart from my own learning to fly, I have used the above approach for 20+ years, quite effectively and have avoided abusing engines by slamming throttles opened or closed, haven't done more than the average number of go arounds, and, touch wood, am yet to spear in!

------------------
ChickenTrainer, on PDL

[Flanker]

Last night I realised it relevant that often on approach in the 737(or any similar) the thrust levers are completely closed anyway.
They are often closed while descending with partial flap and while decelerating after adding flap.This is very evident if there's a tailwind.
Anyway it is instinctive to fly the glide using pitch as you don't really have much choice(if you're tending high at least).In this situation there are usually a few knots in hand to correct the speed decrease if you do pitch up after tending a little low on the slope.
I guess this instinct continues after getting the gear and landing flap out for the last thousand or so feet of the approach.

Tor
I agree that hours are not everything by any means.However I would prefer a fifteen thousand hour sharp pilot to a five thousand hour sharp pilot.
30000 plus hours is one hell of a lot of time whichever way you cut it.John Deakin obviously thinks he has learned something in the time because he writes plenty about it!

[Tor]

I considered this topic closed. But I have to reply to:

<font face="Verdana, Arial, Helvetica" size="2">Chikentrainer

BUT, the aircraft is descending because the lift has been reduced as a result of the primary effect of thrust that is speed.</font>

You don't decend because weight is greater than lift! This is a very commen misconception. You decend beacuse drag is greater than thrust.

<font face="Verdana, Arial, Helvetica" size="2">
If the pitch attitude is maintained, this will cause a decrease in speed and thus lift, which in turn will cause the aircraft to descend.</font>

In the thrust for RoD technique you don't maintain attitude, you let the nose drop, as the aircraft is trimmed, to maintain speed.

[This message has been edited by Tor (edited 05 May 2001).]

[CHICKENTRAINER]

Tor, we might have to agree to disagree.

In part I agree that one descends because thrust is less than drag. Thrust is less than drag, therefore IAS decreases, therefore lift decreases, therefore weight is greater than lift, therefore the aircraft descends.

Personally I trim for an attitude, not a speed.

------------------
ChickenTrainer, on PDL

[Tor]

I'll give you an advice.

Resolve the four forces on a piece of paper. You will find that lift is actually greater that weight in both climb and descend.


------------
Them white fluffy things!

[mitch3p]

AoA is the essence of aircraft control.

From the FAAs Flight Training Handbook (p. 263.);

In a very real sense the Angle of Attack is what flying airplanes is all about. By changing the AOA the pilot can control lift, airspeed and drag. Even the total load supported by the wing may be modified by variations in AOA, and when coordinated with power changes and auxiliary devices such as flaps, slots, slats etc., is the essence of airplane control.

Consider how one flies a glider. All glider control is done by AoA, which is controlled by pitch angle.

Read Stick and Rudder!

Comments?

Mitch

[Propellerhead]

In the RAF UAS I was tought that pitch controls speed / power controls ROD on the d/wind to finals turn (oval circuit), then the opposite on finals! (eg point it at the threshold, keep the aimiming point stationary in the windscreen, and use power to control speed).

Then for my PPL / VFR at Oxford I did pitch controls speed all the time - it worked very well. However, leading up to and on the Seneca this was beaten out of us and told you MUST control speed with power.

The main advantage is that you can aim at the runway, keeping a stable, constant approach path, so important for an ILS.

Now I fly airliners, I can't imagine getting slow going into LHR, and dipping below the glideslope to pick up the speed, then increasing power to get back on the glide!

If you think about it, autopilots and flight director systems use thrust to control speed, and as we folow the FD, this is the way we do it when hand flying. The only time pitch controls speed is during a FIXED thrust manoeuvre (full thrust / idle thrust).

[Tor]

<font face="Verdana, Arial, Helvetica" size="2">Propellerhead

Now I fly airliners, I can't imagine getting slow going into LHR, and dipping below the glideslope to pick up the speed, then increasing power to get back on the glide!
</font>

You could do it a little more coordinated http://www.flightcrew.dk/ubb//wink.gif

[Propellerhead]

Tor, you obviously haven't witnessed my approaches, hee hee! :)

[Ellion]

You must all be from 'blighty' to argue for so long over such an inane subject. All I can say is put the aircraft where you f***ing need to put it and stop thinking so intensly about it, lest you kill me.
Guys, monkeys can physically fly aeroplanes, it's the decision making we're paid for. Don't over stress a mute point!

[Flanker]

Ellion

Whats it to you!

Its a mootpoint, mute is when you can't hear!

[Ellion]

Jeez and I thought it was a condition of not being able to speak!

[Capt Claret]

Well, I'd like to know how many of the subscribers to Power controls Rate of Descent folk, open the throttle wide when they flare to land, so as to reduce their Rate of Descent?

Do tell!

------------------
bottums up !

[This message has been edited by Capt Claret (edited 09 May 2001).]

[Propellerhead]

Tor, lift is actually LESS than weight in a climb as most of the climb comes from the engines eg)thrust. As an extreme, think of an aircraft in a vertical climb, lift = zero, therefore all the climb is from the engines (hence why you don't stall during a wing over in the vertical, despite the speed decreasing to 20 kts or so).

[Tor]

Yes, Propellerhead, your absolutely correct it's less. Went a bit fast writing it - sorry.

The point is that lift is always less regardless if the aircraft is climbing or descending. And not the opposite in climb vs. descend.

Therefore lift doesn't control altitude but thrust does - either excess or deficit.

[This message has been edited by Tor (edited 11 May 2001).]