Ex. 8 - Descending Ex. 8 - Descending

OBJECTIVE What you will learn: How to descend at a variety of airspeeds and power settings to a desired altitude How to accurately level off at desired altitude and establish cruise How to descend to a specified touch-down point. Ex. 8 - Descending

MOTIVATION Why learn this? As with climbs, different situations call for different types of descents Even more variables to consider than for climb (power can be varied) Accurate descents are even more important than accurate climbs. A: For landings! Need to be able to arrive at exact altitude AND exact ground position at the same time. Especially challenging to judge power-off glides: no power assistance! Why? Ex. 8 - Descending

Links You already have understanding of: attitudes and movements power control mixture and carburetor heat control And you learned how make the plane go up… And what goes up, must come down. Ex. 8 - Descending

Let’s see how much you already know: BACKGROUND KNOWLEDGE - TKT Let’s see how much you already know: What mixture setting should be used for descents? What should be carb heat position in a descent? What effect does reducing power have on yaw? How does one control yaw after reducing power? Why? Why? A: Mixture should be enriched prior to a descent. If you leave the mixture leaned and then start descending, the air will get denser and denser, but the amount of fuel going into the carburetor will stay the same, so you’re running the danger of having the engine quit due to insufficient fuel supply! For prolonged descents from high altitudes, mixture can be enriched gradually, rather than all at once. A: For descents at higher power settings, carb heat may remain cold. However, if reducing power well below normal cruise power, put on carb heat to prevent engine icing in a now cooler-running engine. Ex. 8 - Descending

Theories and Definitions THEORIES & DEFINITIONS Theories and Definitions Power-off Descents (Gliding) Gliding: Estimating Range Power-on Descents Power-on Descent Types Ex. 8 - Descending

Power-off Descents (Gliding) THEORIES & DEFINITIONS Power-off Descents (Gliding) What aspects of performance? When might gliding be useful? ATTITUDE + POWER = PERFORMANCE airspeed (how fast we’re going) rate of descent (how fast we’re going DOWN) Where do we find the magical optimal number? Gliding at different speeds x Where do we find the distance we can glide at that airspeed? HOW FAR WE CAN GLIDE This is just like climbing, only the exact opposite: instead of full power we have no power, and instead of going up, we’re going down. When might gliding come in handy? Right, emergency (if engine quits), or if you want to lose altitude quickly. Attitude + Power = Performance. Since power is eliminated from the equation, attitude will determine performance. Namely, what aspects of performance do we care about? Right, airspeed (how fast we’re going) and rate of descent (how fast we’re going DOWN). You can be going very fast without an engine. As fast as you want! But that means that you need to be pointing down. So, you end up not going very far. Or, you can be almost level, but are you going to be flying level? No, without power you’ll be going down, flying at a large… angle of… attack, yes. So again, you won’t be covering a lot of ground. So, somewhere in between “very fast” and “very slow” we have a magical number that allows us to go furthest. And like all the other magical numbers that have to do with the plane, we find this number in the… POH! Keep in mind that we’re making one important assumption here: no wind. Obviously with a headwind you won’t glide as far and with a downwind you’ll go further It does change optimal airspeed for best glide; we will discuss it in more detail in future lessons. Important assumption: NO WIND x x x too slow too fast Distance just right Ex. 8 - Descending

Gliding: Estimating Range THEORIES & DEFINITIONS Gliding: Estimating Range ZERO WIND Will the pilot make that spot? ***Come back to this later and change to a better picture sequence! More windshield, higher eye level, less instrument panel!*** A pilot here decided to practice his gliding technique. He wants to try gliding to this spot. *click* The airspeed is pegged at best glide. Let’s take snapshots every 500 feet. *click* *click* *click* A: No. How do you know? Use a spot or mark on the windshield, and see what your desired touchdown spot is doing with relation to that mark. If it’s moving down, you’re overshooting the target. If it’s staying still, you’re going right for it. And if it’s creeping upwards, you’re not going to make it… What can the pilot do to stretch the glide? Ex. 8 - Descending

Gliding: Estimating Range THEORIES & DEFINITIONS Gliding: Estimating Range Plane is already flying at best gliding speed! Raising the nose will: NOTHING! shorten your gliding distance AND make your airspeed to dangerously low ***Come back to this later and change to a better picture sequence!*** Trick question… NOTHING! NEVER TRY TO “STRETCH” A GLIDE. Ex. 8 - Descending

Power-on Descents Normal descents are power-assisted THEORIES & DEFINITIONS Power-on Descents How much power? Normal descents are power-assisted Power = more choice for performance +/- 100 rpm = +/- 100 feet per minute or +/- 100 rpm = +/- 5 knots. With power off, each airspeed corresponded to a set rate of descent Now you change rate of descent and airspeed independently A: Depends on the performance you want. Can be anything between idle power and normal cruise power. Ex. 8 - Descending

Power-on Descent Types THEORIES & DEFINITIONS Power-on Descent Types Landing Approach stabilized descent at specific airspeed to touchdown at specific point Enroute no hurry to lose altitude more comfortable for passengers Power setting Carb heat Airspeed Flaps Usually below green arc (about 1500-1900 rpm) Above green arc (100-300 rpm below cruise power) HOT COLD See POH (55-65 knots in Cessna 150) Close to cruise speed Up (enroute descent done at high speed, low rate of descent – no need for additional lift and drag) Down (for better forward visibility and lower safe descent speeds) Ex. 8 - Descending

Procedures “Downwind” Check Power-off Descent Approach Descent Entry During Approach Descent Enroute Descent Recovery from Descents Leveling out Overshoot. Ex. 8 - Descending

“Downwind” Check Oil Temperature and Pressure in the green PROCEDURES “Downwind” Check Oil Temperature and Pressure in the green Primer in and locked, Master ON, Mags on BOTH Circuit Breakers in, Ammeter Needle right, Overvoltage Light OFF Carb Heat hot, Mixture rich Fuel ON, gauges show sufficient fuel Flaps UP Brake pressure. Ex. 8 - Descending

Power-off Descent: Entry PROCEDURES Power-off Descent: Entry Cockpit check: oil T+P in the green, carb heat hot, mixture rich Look-out! How will power reduction affect yaw? Power Attitude Trim smoothly reduce power to idle maintain cruise attitude until airspeed reaches best glide set descent attitude for that airspeed You have it down PAT retrim airplane Ex. 8 - Descending

Power-off Descent: During PROCEDURES Power-off Descent: During Keep good look-out Maintain coordinated flight with rudder Maintain straight flight with ailerons Every 500 feet smoothly add full power, then reduce back to idle A: Adding a burst of power every 500 feet will help keep the engine warm. This is especially critical in cold weather. Why? Ex. 8 - Descending

Approach Descent: Entry PROCEDURES Approach Descent: Entry Cockpit check: oil T+P in the green, carb heat hot, mixture rich Look-out! Power Attitude Trim smoothly reduce power to 1500-1900 rpm maintain cruise attitude until airspeed enters white arc once airspeed is “in white”, extend flaps set descent attitude for approach airspeed (see POH) retrim airplane Ex. 8 - Descending

Approach Descent: During PROCEDURES Approach Descent: During Keep good look-out Maintain coordinated flight with rudder Maintain straight flight with ailerons Control attitude and airspeed with pitch Control descent rate with power. Ex. 8 - Descending

Enroute Descent: Entry PROCEDURES Enroute Descent: Entry Cockpit check: oil T+P in the green, mixture rich Look-out! Power Attitude Trim smoothly reduce power to 100-300 rpm from cruise establish descent attitude at near cruise airspeed retrim airplane Ex. 8 - Descending

Enroute Descent: During PROCEDURES Enroute Descent: During Keep good look-out Maintain coordinated flight with rudder Maintain straight flight with ailerons Control attitude and airspeed with pitch Control descent rate with power. Ex. 8 - Descending

How will adding power affect yaw? PROCEDURES Leveling Out Begin leveling out at 10% of rate of descent If climbing up to 3500 feet at 300 feet per minute, begin leveling out at… Continue look-out! smoothly add power to approximately cruise setting carb heat cold Power Attitude Trim How will adding power affect yaw? return airplane to cruise attitude A: 10% of 300 is 30, so begin levelling off 30 feet prior to your desired altitude; i.e., at 3470’. A: Adding power will cause the plane to yaw to the left, so be prepared to put in that right rudder! retrim airplane Ex. 8 - Descending

Overshoot! Power Attitude Trim full power carb heat cold PROCEDURES Overshoot! Power Attitude Trim full power carb heat cold Why retract some flap right away? flaps up to 20o set up a climb at 55 knots wait for +’ve rate of climb on VSI flaps up in stages A: Flaps add drag, especially flaps in the 20-40 degree range, so retracting the flaps to 20 degrees will help your climb A: Flaps also add lift, so retracting flaps all at once may cause the plane to stall. Why not retract all flap at once? retrim airplane. Ex. 8 - Descending

Considerations Effect of Flaps Effect of Wind. CONSIDERATIONS Ex. 8 - Descending

Effect of Flaps on Descent CONSIDERATIONS Effect of Flaps on Descent More lift can safely descend at lower airspeeds More drag steeper descent given same airspeed More nose-down attitude better forward visibility given same airspeed Airspeed must be in white arc before flaps are extended! We’ve got a runway… We’ve got some obstacles! So even at your steepest approach angle, you end up wasting lots of runway length! Wouldn’t it be nice if you had a way of making your approach steeper, so you could go over the obstacles like this. Well, there is! Flaps! Ex. 8 - Descending

CONSIDERATIONS Effect of Wind In headwind: can glide further by increasing airspeed slightly (offset effect of wind pushing you back) In tailwind: can glide further by decreasing airspeed slightly (take advantage of lower rate of descent at slightly lower airspeed) TAILWIND NO WIND HEADWIND x x x x Ex. 8 - Descending

SAFETY Cockpit check before all descents Carb heat: on for any descent at rpm below green arc Engine warm-up: every 500 feet during glides Glides: never try to “stretch” Flaps: airspeed must be “in the white” Constant look-out! (for other traffic and obstacles.) Ex. 8 - Descending

What is its significance? REVIEW Review: What is your airplane’s best glide speed? During an approach to landing your intended touchdown spot is drifting up. What does that mean and how do you fix the situation? Same as above, but the spot is drifting down. What is its significance? Ex. 8 - Descending

CONCLUSION Conclusion: As you can see, even seemingly simple procedures involve a lot of details and considerations. But all the different procedures and considerations are related, and we keep coming back to the basic principles from earlier lessons. Today you learned about one of the most fundamental and important flying skills. After practicing this lesson, you will be well on your way towards learning to land! Read for next lesson: Ex. 9 – Turns. Ex. 8 - Descending