Over the fence throttle setting
 

On light civil aircraft...Chop power and glide or reduce power all the way to flare?

It depends on wind/gusts, runway, type of aircraft, flap setting, and a lot of other factors.

Chop the power and glide in a Seneca (also a "civil light aircraft") and the result might look like this: Seneca landing accident image by Bartuzzinni on Photobucket

Power off as the aircraft goes through level in the flare.
The slipstream adds to the airflow over the tailplane so if you close the throttle before or at the start of the flare the nose will go down just when you want to raise it - not a helpful thing for it to do.

HFD

You forgot to mention the fact that closing the throttle will also cause Yaw - and as a consequence roll. However, the only people who should see these reactions are those that can't rememebr exercise 4 (and if they can't are not reminded by their instructor).

Provided that the pilot prevents pitch, roll and yaw while changing power there is no reason why making changes to the power setting (increase or decrease) at any stage of the approach or landing should cause any form of an unexpected unwanted or unstable situation.

-------

Getting back to the original question and by "over the fence" I expect that you mean a point 50ft above the threshold i.e. the official end of the approach and the start of the landing phase (the start of the landing distance required).

The first place you need to look is the performance section of the Flight Manual / POH. This will tell you the exact conditions from which the performance figures were derived. Many of the older manuals with say something like "Power Off Approach at 67Kt, Flaps 40, Full Stall landing, maximum braking, paved dry level runway.

Clearly from this you can see what you have to do to have any chance of getting close to the figures quoted in the manual. and ultimately isn't this what we are trying to do rather than simply making some form of random arrival that hopefully permits us to use the aircraft again with minimum fuss?

The next thing that we have to think about is making a good stable approach.

If you are making a glide approach then it is easy.

If making an approach with power then the question is can you cope with a destabilisation at 50ft (which for most aircraft is before the flare is entered) by removing a lot of the energy and since there is no way the aircraft will continue some 300m forward while remaining on a 3 degree slope (or follow any other power on profile to the aiming point) unless you have a lot of excess speed. This means if you chop the power at 50ft you are going to have to lower the nose and quite soon thereafter raise it again for the flare.

My recomendation is that the aircraft is flown along a stable approach with power towards the desired aiming point at a constant approach speed / approach angle and will cross the threshold at 50ft. From a suitable point the power is slowly reduced while continuing towards the aiming point so that the aircraft enters the flare power off and has an arrival on the mainwheels (tricycle) without damaging them and without any significant float.

The last time you look at the speed is just at the 50ft point and this is your energy indicator -

significantly low - go arround

slightly low - delay the power reduction

on speed - good

slightly high - earlier then normal power reduction

significantly high - go arround.

After 50ft, you are no longer interested in approach speed because you are no longer on approach. You are however interested in the aiming point and making a suitable arrival. Keeping everything stable and making changes gradually makes this much easier.

Since this will not be the method used to derive the landing figures in the manual you need to go into the figures and work out what to add - this is not difficult. If one looks at the airbourne part of the figures in the manual one will usually find that it is a lot less than 300m (1000ft) - 3 degree distance from 50ft to 0 - .....because either a glide approach was made or the throttle was chopped at 50ft. Simply add the missing distance to the book figures and you have a more resonable starting point for your performance. Don't forget to still add suitable factors!!

In sumary - stable approach at the correct approach speed followed by a gradual reduction in energy while making progress towards the aiming point.

"You forgot to mention the fact that closing the throttle will also cause Yaw ... " actually, I didn't forget. I chose to mention the significant effect and to ignore the insignificant ones.
We all have different experiences, but mine are that good landings tend not to follow power reductions at the start of the flare.

HFD

When doing type ratings on the PBY I had them reduce power to throttles closed at two hundred and fifty feet during water landings.

When they could consistently land without having to add power I then allowed use of power for landing.

During water landing training the circuits were at three hundred feet and three minutes touch and go to touch and go...they did thirty minutes of T&G's which made for ten circuits.

Fly beta for me.....

I agree with Chuck about cutting the throttle early and learn to land that way.

If you can't make consistently good landings from a glide approach, keep doing it until you can.

In my opinion there is no "magic point" where you close the throttle. If you are looking for one it probably reveals that you still don't have the "feeling" for your aircraft type. More hours/training might be appropriate (but not to find out where to cut the throttle).

Deliberately flying a three degree slope for a light trainer such as a C172, Warrior etc is nonsense. A typical glide approach with idle power and landing flap down will be around six to seven degrees and that is quite normal. These aircraft are so light they have little inertia and using the flight manual recommended threshold speed, the flare is straightforward. A powered final approach with typically 1200-1500 RPM and landing flap will give around 5-6 degrees descent angle. To deliberately aim for a transport aircraft three degree ILS slope while flying a light single as above (landing flap selected) would need considerable RPM requiring a long drag in at low speed. Three degree slope was never designed for light aircraft.

Hello!

Objection! As an instructor, I mainly train students on integrated ATPL courses. Pedestrian to Airliner talkes less than 200 flying hours, nearly half of which are "flown" on a procedures trainer (not very realistic in the last stages of landing). So we fly every single approch exactly the way they will fly it later on the job, independent of the type of (training) aircraft to familiarise them early with the approach picture they will see after they complete their course. Nobody ever called this nonsense before...

Happy landings,
max

Is it? Perhaps we are heading down the wrong road in FAR-23 and CS-23 then!

I am all for glide approaches (subject to engine care). However, one has to remember a few things.

1. The 3 degree slope has been round a lot longer than "heavy" aircraft or even jets. the 3 degree slope comes from a lot of research into what pilots felt was a "natural" approach angle.

2. When teaching approach and landing techniques to students the most important thing is the stable approach angle and being able to recognise not only the basic approach angle but also to be able to make appropriate adjustments when visual illusions (up-sloping or down sloping runways for example or wide vs narrow runways) may make assessment of the correct safe approach angle more difficult.

It is in the teaching environment that being able to repeat a standard over and over assists the student in many ways - even if they have no plans to fly professionally.

Flying glide approaches are an essential progression once the basics have been mastered. However, it is only when the basics have been mastered that one can expect the student to cope with the situation where the perfect approach will have one runway aspect today and a totally different one tomorrow to the same runway and in fact one can fly a series of perfect glide approaches where one never has the same runway aspect.

(Almost) Every instructor I know can stand up at a board and draw 3 diagrams - the runway aspect when On the slope, when high and when low and you will find that in 99.9 of them they will draw a 3 degree slope or very close to it.

Now, can you draw me the runway aspect for the glide approach, (on, high and low) - oh......and do it for calm, 5Kt 10Kt, 15Kt, 20Kt and 30Kt of headwind plut 5Kt of tailwind.......I'll be back in a few hours to review the 21 drawings you will have made!! :E

Having said all that - if you refer back to the post you read before making these comments, you will find that I was making a reference to landing distances and giving a few pointers on how one needs to compare the technique one is using on the day to the technique used to establish the book figures. As I pointed out and I am sure you will find, if one tries to use a 3 degree slope after the 50ft point one will exceed the book figures because they are not based on such a slope.

Let me finish by quoting what I said previously;

Where do you get 3 degrees from that?

As long as your students are never allowed out unsupervised in a SEP I don't have a problem with that. I think it is nonsense as well.

So you fly 3 deg glidslopes cause thats what they will be used to flying commercial. Must have quite talented limited students then cause all the low houred modualar FO's I have flown with haven't seemed to have had any issues with doing three degree glides.

Its just the usual pish of operating SEP like a big jet which doesn't teach them how to fly properly and also fills there head with rubbish.

You will be telling us next you make them add on half the gust to the approach speed.


If they wish continue flying SEP I hope they go for further training before being licensed to fly unsuspecting pax.

I teach as written in our authority-approved training manual. And yes, it asks for 1/2 gusts to the approach speed (but not more than 15kt in case of C172/Pa28).

Thus another generation of pilots is pumped out the sausage machine who don't have a clue what they are doing and there heads are full of rubbish.

Lets just hope they all get jet jobs so they can continue to be operators instead of pilots. And also not put anyones life at risk in a single engine piston.

I don't know what FAR-23 and CS-23 are saying, but if they tell you to teach 3 deg approaches in a light aircraft they must be wrong and you should lobby the "authorities" to change them rather than blindly accept them as the "truth".

To teach a student to fly an aircraft in an unsafe manner with the excuse that he otherwise will have problems to convert later is really daft. If a student is airline pilot material i believe he won't have a problem to convert. If he has a problem he should probably not be a pilot at all, or at least he should learn how to land a light aircraft safely since this might be the only type of aircraft he will fly in the future.

I was taught flying at an airfield with houses, trees and no open fields on the approach. Do you think my instructor took the risk of teaching me to approach at 3 deg because FAR-23 and CS-23 said so? No he didn't, he taught me to use common sense and land the aircraft safely.

Remember: Every approach is potentially a glide approach.

Hmmm.... going back and reading my post #6, from some of the assertive opinions here it would appear that I am a poor instructor who needs retraining to teach the correct way.

Intercepted,

Recomend that you find out what FAR-23 and CS-23 are and then review your post.

As an instructor, can you please let us have a drawing of the runway aspect you teach for whatever constant angle of approach you use in SEP - (day and night). You can let us know how we can recognise that aspect and know that we are not too high and not too low especially when flying an SEP at night. ;)

----------

Every safe operator I know make an appropriate addition to the approach speed when flying in gusting and/or turbulent conditions.

Most of those same operators use the POH speed when there are no gusts and impose something like a +10 / -0 tollerance on approach speed.

It is receomended by ICAO, FAA, CAA, EASA and last but by no means least the Aircraft Manufacturer.

Show me a "pilot" who can maintain an approach speed and no less when the windspeed varies between 5 and 25 knots.

People would do well to remember that the reported wind is an average speed and you get the gust if it is more than 10 knots above the average. Therefore a wind moving rapidly between 5 and 15 knots is reported as 10Kt. If there are gusts that reach 21 then it is 10 Gusting 21. So we add on 5 or 6 knots during the approach phase because if the wind drops from 21 to 5 that is a 16 Knot loss and having 5 knots in hand is a very good idea.............even more so when flying a type where that 16 Knot loss can represent 30% of your stall speed..............now go on and tell me you will approach at 1.3Vso even when it is gusty!!!

Problem also is that many people fail to understand where the approach ends and the landing begins and that flying the approach with an extra 5 knots due to gusts does in no way means that the landing phase has to be flown 5 knots faster than normal.

That is where the total lack of understanding happens and I see it at all levels - people adding the appropriate increment to the approach speed but making the error of maintaining the extra speed all the way to the flare without realising that the approach ended some distance behind them while at the same time not allowing extra landing distance for the overspeed at the threshold.

As I said earlier. Approaching 50ft check your energy (speed) and based on that decide how soon or late you will start to close the throttle.

Most of the time I instruct instrument flying. Mostly on single engine piston aircraft. Most instrument approaches have three degree glideslopes (both precision and non-precision approaches). If I interpret your statement correctly, I must conclude that instrument flying on single engine aircraft is inherently unsafe and should not be taught. Are you really saying that?

Well it is thats why nearly all authorities ban single engine IMC IFR flights public transport.

Alot of the airports in the UK 3 degree approaches don't allow you to glide clear in case of engine failure. You maybe lucky where you are training.

The additional "risk" for training flights is deemed acceptable because everyone onboard knows about the increased risk because its a means to an end ie to complete the training course.

The only time a single is mean't to use a 3 deg glide outside training is when the risk to life and limb is increased due to other factors ie you can't see the ground due IMC and you have to get it on the ground before you run out of fuel. If you have the option to fly it visually you should decrease your exposure to risk by flying it visually with the normal SEP approach angle.

Can anyone come up with any form of reference that backs-up such a statement or that in any way defines what "the normal SEP approach angle." is?

There is plenty of litrature available to explain why 3 degrees was selected as a standard point to start from.

There are published rules that define approach angles above 4.5 degrees as "steep approaches" and they don't limit that definition to certain categories of aircraft if such approach angles have to be used.

Can't find anything that defines this "normal SEP approach angle." as being any different from any other aircraft.

Can you?

Perhaps we are getting confused with "optional" techniques and "emergency procedures" when we simply want to define some yard-stick that a student can refer to and 99% of instructors can easily recreate.

Applies to a lot of multi-engine types also especially when close to their certified MTOW. So it is not a single engine issue.

Indeed, the CAA has seen fit to exempt all aircraft landing and taking-off at those aerodromes from the low flying prohibitions and they do not agree that a C172 flying a 3 degree approach could be classed as anything other than "flying in accordance with normal aviation practice".