Glide descent leveling off technique
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Regarding the origional question, whether to set pitch attitude at or slightly above cruise attitude.
The difference is minor, because if you start adding power approx 50 ft before desired altitude (10 % VSI in a C172) the spead will build up quickly. And in all reality, when I glide at 65 KIAS my attitude is approximately cruise attitude so I barely need to change it at all as I level off. The power increase will absorb and neutralise the ROD until I am stabilised at my desired altitude with 0 vertical speed. That's also why I teach (or my FTO rather) full power, the acceleration will go quicker and there will be less need to change pitch attitude as I accelerate.
Works well IMO, many ways to skin a cat though...
PS. Don't forget right rudder, reduce as you accelerate
The difference is minor, because if you start adding power approx 50 ft before desired altitude (10 % VSI in a C172) the spead will build up quickly. And in all reality, when I glide at 65 KIAS my attitude is approximately cruise attitude so I barely need to change it at all as I level off. The power increase will absorb and neutralise the ROD until I am stabilised at my desired altitude with 0 vertical speed. That's also why I teach (or my FTO rather) full power, the acceleration will go quicker and there will be less need to change pitch attitude as I accelerate.
Works well IMO, many ways to skin a cat though...
PS. Don't forget right rudder, reduce as you accelerate
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It may be academic but it is important to understand what is going on. I spend my life flying with pilots who set a power and an attitude and then seem to take another five minutes fiddling with throttle and trim because they haven't previously thought about what is happening. When they finally reach some form of stable state they then realise they are not at the altitude they want. So we then get the pitch up/down scenario together with associated airspeed change and the whol cycle starts over.
Who do I blame? Instructors wh will sign-off an Ex 6-8 in less time than it has taken to pen this message.
Who do I blame? Instructors wh will sign-off an Ex 6-8 in less time than it has taken to pen this message.
It may be academic but it is important to understand what is going on. I spend my life flying with pilots who set a power and an attitude and then seem to take another five minutes fiddling with throttle and trim because they haven't previously thought about what is happening. When they finally reach some form of stable state they then realise they are not at the altitude they want. So we then get the pitch up/down scenario together with associated airspeed change and the whol cycle starts over.
Who do I blame? Instructors wh will sign-off an Ex 6-8 in less time than it has taken to pen this message.
Who do I blame? Instructors wh will sign-off an Ex 6-8 in less time than it has taken to pen this message.
The longer I instructed the more time I spent on the foundation exercises. I was looking at my instructor records the other day. The trend is a longer time to solo but a shorter time to the PPL flight test and IMHO a lot better product at the end because of the time and effort I spent on getting the basics right at the beginning.
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they then realise
What would we think as the passenger of an experienced driver, who, while approaching a stop in a turning lane, braked a bit while driving straight, then turned a bit with no braking, then signalled, then turned a bit more, then drove straight and braked more and so forth? No, we expect a fluid motion of the aircraft, resulting from appropriate and combined use of the controls.
Sure, when you're getting used to used to a new machine, you may take a few tries at it to demonstrate that fluid motion, but it's what you aspire to.
So it's not "do this, then that.... and so forth". It's transition from this phase of flight to that, while maintaining or changing speed, altitude, configuration as needed, and not exceeding any operating guidelines, or limitations. Other than that, making a recipe out of it is just compicating something which should be very simple and natural.
For all you normally aspirated piston pilots who doubt me, take sticky notes, obscure airspeed indicator, and tachometer, and go flying. You'll find you're more smooth, without the distraction of chasing numbers on instruments!
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Originally Posted by Pilot DAR
For all you normally aspirated piston pilots who doubt me, take sticky notes, obscure airspeed indicator, and tachometer, and go flying. You'll find you're more smooth, without the distraction of chasing numbers on instruments!
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If you are descending at the best glide speed you are in danger of ending up on the backside of the drag curve with the OPs instructors method-that might be OK with more powerful aircraft but for light singles near the ground in my opinion thats not best practice
An ex-airforce instructor tought this method of level off from glide descent - it seems this is the technique used in airforce PC7.
Assume glide descent speed is 70kts, cruise is 100kts.
- Initiate level off when 10% ROD of desired altitude.
- Simultaneously select full power and slightly higher than straight & level attitude.
- As airspeed increases, progressively lower the nose to straight & level attitude.
- 5kts before reaching cruise speed of 100kts, select cruise power.
- Hold straight & level attitude
- Trim
The main difference in this technique is that you select slightly higher than s&l attitude initially, then progressively lower to s&l attitude as airspeed reaches 100kts.
His reasoning is, as you are in a glide descent at 70kts, when leveling off if you select s&l (instead of slightly higher), you will still be descending due to the lower airspeed initially.
Any thoughts on this technique?
Assume glide descent speed is 70kts, cruise is 100kts.
- Initiate level off when 10% ROD of desired altitude.
- Simultaneously select full power and slightly higher than straight & level attitude.
- As airspeed increases, progressively lower the nose to straight & level attitude.
- 5kts before reaching cruise speed of 100kts, select cruise power.
- Hold straight & level attitude
- Trim
The main difference in this technique is that you select slightly higher than s&l attitude initially, then progressively lower to s&l attitude as airspeed reaches 100kts.
His reasoning is, as you are in a glide descent at 70kts, when leveling off if you select s&l (instead of slightly higher), you will still be descending due to the lower airspeed initially.
Any thoughts on this technique?
If the object is to descend from one altitude to another (particularly in the context of cross country flight) than the most efficient way is to simply leave cruise power on and set a nose down attitude that will give you a 500 foot per min decent rate.
I also agree with PILOT DAR's point about "feeling" the aircraft. How ever what a 6000 hr test pilot can do with unconscious competence is a little harder for a 60 hour brand new PPL
. But his point is still valid and this is what every low hour pilot should strive for.Straight and level, climbing, descending and, turning are the foundation exercises of flight training. Key to success in each, is attitude control. So in the context of descending, to fly accurately and smoothly the pilot must know what attitude to go to and then the amount of power set will give him the right performance. Sounds easy but in practice is IMO an often imperfectly learned skill. Too often climbing or descending involves pitching the nose up or down to a random attitude and accepting what ever results.
This is where covering the ASI in flight is a great exercise. Start with the simplest manoever, full power Vy climb. After covering the ASI pitch up to what you think is the right attitude to result in the Vy airspeed, let the aircraft stabilize and trim. Then uncover the ASI, adjust the attitude as necessary and repeat. It is amazing how quickly you will find you can nail the attitude which will result in exactly the Vy airspeed without ever looking at the ASI. Now do the same for the power off glide. Knowing this one is really important in the event of an engine failure, and then start picking random combinations of airspeed and power. Some dedicated practice will produce a situation where flying goes from random control inputs to the "feel" of a truly proficient pilot.
Sadly, more and more pilots are afraid to fly VFR in 50+ km visibility without an artificial horizon, let alone airspeed indicator. 
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I had the delight yesterday to be asked to do the maintenance test flight on a Tiger Moth. It had not flown in 7 years. I was surprised to find that it did have an airspeed indicator in the panel (I still liked the one on the wing strut though - easier to read!). I had to check myself out, as there was no one else available to fly it.
Wanting to be very gentle on the 70 year old engine, but still being weary of it quitting (with no undershoot area), I did high, power on, full sideslipped approaches, so if it quit, I could still make the runway. The airspeed difference between cruise, approach and flare does not seem to be that great in the Moth anyway, so planning descent speeds seemed un-necessary. I just flew it by feel, and it worked out fine.
Trim? Haha!
Wanting to be very gentle on the 70 year old engine, but still being weary of it quitting (with no undershoot area), I did high, power on, full sideslipped approaches, so if it quit, I could still make the runway. The airspeed difference between cruise, approach and flare does not seem to be that great in the Moth anyway, so planning descent speeds seemed un-necessary. I just flew it by feel, and it worked out fine.
Trim? Haha!
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Think about the reverse, a level off. You climb at say 110kts but want to end up at 140kts. As you approach the height you require (QFE set !!!) you set the att required for initially 110kt cruise (as that is the speed you are at) and then as you accelerate you need to lower the nose (and TRIM) as the att required for the 140kt cruise will normally be lower than a 110kt cruise.
The situation described is essentially the same in reverse. There is no mention as to why they are in a glide descent and the use of full power would indicate to me that they are not paying for the fuel (military training?) however the technique is correct and works on many different types, JP5, Hawk, Grob, PC7, Tucano, CT-4E in my experience !
The situation described is essentially the same in reverse. There is no mention as to why they are in a glide descent and the use of full power would indicate to me that they are not paying for the fuel (military training?) however the technique is correct and works on many different types, JP5, Hawk, Grob, PC7, Tucano, CT-4E in my experience !
Think about the reverse, a level off. You climb at say 110kts but want to end up at 140kts. As you approach the height you require (QFE set !!!) you set the att required for initially 110kt cruise (as that is the speed you are at) and then as you accelerate you need to lower the nose (and TRIM) as the att required for the 140kt cruise will normally be lower than a 110kt cruise.
The situation described is essentially the same in reverse. There is no mention as to why they are in a glide descent and the use of full power would indicate to me that they are not paying for the fuel (military training?) however the technique is correct and works on many different types, JP5, Hawk, Grob, PC7, Tucano, CT-4E in my experience !
The situation described is essentially the same in reverse. There is no mention as to why they are in a glide descent and the use of full power would indicate to me that they are not paying for the fuel (military training?) however the technique is correct and works on many different types, JP5, Hawk, Grob, PC7, Tucano, CT-4E in my experience !
Also, essentially you are doing straight and level part 2 and you can make a distinction as to whether you want to accelerate rapidly to the target speed (when levelling off from a glide in the OP's query) - which case initially select full power - or desiring to accelerate slowly to the target speed, in which case select cruise rpm (with slight correction for fixed pitch as rpm will increase as airspeed increases).
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But what puzzles me with all this is why you would be descending at 110 kts to have to accelerate to 140?
In most cases descending to a level and you are more likely to be at 160kts when you arrive at the target speed ie with cruise power set you will sit there waiting for the speed to bleed off to the 140 kts.
Climbing is different as you will be below cruise speed you will have a higher AOA and more drag as you level and you maybe at full power?
Pace
In most cases descending to a level and you are more likely to be at 160kts when you arrive at the target speed ie with cruise power set you will sit there waiting for the speed to bleed off to the 140 kts.
Climbing is different as you will be below cruise speed you will have a higher AOA and more drag as you level and you maybe at full power?
Pace
