OCKPIT CLASSROOMBy Harold Holmes

Department of Safety Studies Injury Research LaboratoryUniversity of Wisconsin-Whitewater, Whitewater, Wl 53190

Probably the most difficult maneuv-ers for applicants to perform properlyon a flight test are the short field takeoffand landings tasks. The major difficul-ties on takeoffs appear to be over-con-trolling, failure to make corrections forasymmetrical thrust or P factor, impro-per power settings and performing thelift-off at the incorrect airspeed. Theshort field landing poses the problemsof airspeed control, making a controlledapproach with power, selecting a suita-ble touchdown point (within 200 feet ofa specified point), maintaining direc-tional control during and after landingroll and braking in the shortest distanceconsistent with safety. The newly is-sued Private Pilot Practical Test Stan-dards (FAA-S-8081-1) provide CFIs,examiners and student pilots the stan-dards necessary to evaluate short fieldprocedures. They are excellent stan-dards by which to evaluate pilots on allmaneuvers.

When a short field takeoff is per-formed it is assumed not only that therunway is short, but that there are obs-tacles, e.g., tall trees, at the end of therunway. In view of this, the takeoffshould be performed in three separatephases. In the first phase, you will wantto become airborne as quickly as possi-ble. The purpose for this is to allow theairplane to accelerate to the manufac-turer's recommended airspeed (Vx) attakeoff and maintain it until the obstacleis cleared. Flying in the ground effectafter leveling off just above the runwayis a procedure that will allow you toreach Vx sooner. Secondly, when therecommended airspeed is reached, youwill start to climb at the best-angle-of-climb (Vx) until the obstacle is clearedor until at least 50 feet above the sur-face and then accelerate to Vy andmaintain Vy plus/minus 5 knots as thestandard implies.

The objective is to achieve themaximum gain in altitude in the shortestdistance traveled, making it possible to

clear the obstacle (trees) — see Dia-gram I. Since short field takeoff proce-dures vary among manufacturers andpilots, the following procedures outlinedin the Haldon Books, Inc. Flight Man-euvers Manual provide only those basicrules that may be applied to allairplanes (see Diagram 2).

In tail wheel type airplanes the tailshould be raised off the ground slightlywith the elevator, held at a tail low flightattitude and maintained until proper lift-off or rotation airspeed is attained.

During the third and final phase of theshort field takeoff, and once the obsta-cle is cleared, assume the proper climbattitude at Vy and retract flaps and gear.As the flaps are retracted it is necessaryto increase the angle of attack. Re-member to trim for your airspeedthroughout the maneuver — this willmake it easier for the pilot.

Now for the correct procedure whentaking off from a rough, soft or snowcovered field. This is quite different fromtechniques appropriate for short fieldswith firm, smooth surfaces. Again, useflaps as specified in the manufacturersmanual for takeoffs under these ad-

SHORT FIELD TAKEOFFObjective: To takeoff on ashort runway in the shortestpossible distance and to clearobstacles at the end of therunway.Use maximum available areaand align airplane with centerline at extreme end of runway.or field.Thorough pre-takeoff check.Check carburetor heat, flaps.trim tab, and check for fullpower.

GROUND ROLLUse m a n u f a c t u r e r ' s recom-mended flap setting, airspeedand procedures.• Flaps —• Carburetor heat — COLD• Full throttle• Climb speed — Vx (Best

angle of climb to clear ob-stacle)

Hold brakes until maximumtakeoff power is attained.(Optional)

Set trim to Vx climb attitudeairspeed.

PROMPT SMOOTH APPLICA-TION OF MAXIMUM ALLOW-ABLE POWER.

Takeoff involves little or nouse of the elevator control —neutral position recommend-ed. Check Airplane FlightManual.

DIAGRAM 2

tj

verse conditions. In this case, theweight of the airplane should be trans-ferred as rapidly as possible from thewheels to the wings as the take-off rollproceeds. There are six considerations,from a safety standpoint, to determinewhether or not a safe departure is pos-sible:

1. Runway length and obstacles tobe cleared.

2. Field elevation.3. The temperature (compute density

altitude).4. The aircraft weight — the lighter

the load the shorter the takeoff roll.

CRUISE CLIMB• BEST COOLING AIRSPEED• MAXIMUM GROUNDSPEED

BEST RATE OF CLIMB VyGREATEST INCREASE IN ALTITUDEIN A UNIT OF TIME

BEST ANGLE OF CUMB VnBEST OBSTACLE CLEARANCEGREATEST INCREASE INALTITUDE IN A GIVENDISTANCE

DIAGRAM 1

30 MAY 1985DIAGRAM 3 CLIMB PATHS UNDER DIFFERENT WIND CONDITIONS

SHORT FIELD LANDINGAssume 50 foot obstruction using final approachspeed which will result in little or no floating afterthe throttle is closed during the flare for touch-down.

Reduce power, partialHaps, gear down.cull flaps, establish appreach angle and airspeed. xv*

I KEY POINT -i-oCORRECT PERFORMANCE1. Approach speed is 1.3 times power-oft stalling

speed. Carry power until the point of steep de-scent landing past obstacle.

2. Touchdown on mam wheels with power on atas slow a ground speed as possible. Minimiumfloating.

3. Close throttle immediately after touchdown.4. Retract flaps and brake (see manufacturer's

recommendations).

DIAGRAM 5

5. Wind — A headwind componentwill reduce the groundspeed necessaryto produce the takeoff airspeed. Also alack of headwind will increase thegroundspeed necessary to reachtakeoff airspeed. Once airborne a head-wind will allow the pilot to climb at asteeper angle making it easier to clearthe obstacle (see Diagram 3).

6. Runway Condition — The slope ofthe runway, condition of the surface, up-slope or downslope will all affect takeoffdistance. A grassy surface will producemore rolling friction than a hard surface,whereas a wet surface with puddles ofwater or snow will produce an increasein rolling friction. Anything that in-creases rolling friction will also increasethe takeoff distance.

The weight transfer is done by usingthe elevator control to maintain a nosehigh attitude. The nosewheel should belifted clear of the surface as soon as theelevators become effective. Since theairplane is held at a relatively high angleof attack throughout the takeoff run, thewings will progressively relieve thewheels of more and more of theairplane's weight, reducing the dragcaused by surface irregularities. If theproper attitude is maintained theairplane will lift-off at the minimum pos-sible airspeed which is slower than asafe climb speed. This can be ac-complished because of the helping ac-tion of ground effect. When lift off oc-

curs and the wheels are just clear of thesurface, the angle of attack should bereduced gradually until the best angleof climb airspeed is achieved beforefurther climb is initiated. If there is anobstruction which must be cleared fol-lowing a short field takeoff, the climbmust be performed at Vx, the best angleof climb speed. At no time should theairspeed become slower than the bestangle of climb speed (see Diagram 1).

I have noted other typical errors as-sociated with short field takeofftechniques such as premature rotation,incorrect takeoff speed and too abruptpull-ups. A premature or excess rotationwill greatly increase drag, causing a de-crease in acceleration. This actually re-sults in a significant increase in takeoffdistance — a poor procedure for anytakeoff, especially a short field one.Another hazard which can be createdis induced drag increasing duringtakeoff and causing a reduction inairspeed which could make the situationripe for a stall and subsequently a spinat a low altitude.

The same remarks that can be madeon flying technique and basic principlesconcerning short field takeoffs alsoapply to a short field approach and land-ing. The approach must be performedto provide a stabilized, steady flightpath to the intended point of touchdown.The new FAA Private Pilot PracticalTest Standards call for a touchdownbeyond and within 200 feet of aspecified point, with little or no float andno appreciable drift and the airplane'slongitudinal axis must be aligned withthe runway centerline. Then, after land-ing, the directional control must bemaintained after which comes the appli-cation of braking and controls neededto stop in the shortest distance consis-tent with safety (FAA Practical TestStandards, 1984) — see Diagram 5.

As in short field takeoffs, the shortfield landing is one of the most criticalof the maximum performance opera-tions (TASKS), since it requires one tofly the airplane at one of its crucial per-formance capabilities while close to theground in order to safely land withinconfined areas (FAA 1980). This lowspeed power-on approach is closely re-lated to the TASK of "Flight at MinimumControllable Airspeeds" which is an im-portant proficiency flight maneuver.

It is imperative that the proceduresrecommended in the airplane flightmanual be used for short field landingsover assumed 50 foot obstructions.The Video Training Aids, Inc. tapesstress the fact that short field proce-dures involve the use of full flaps withgear extended on final approaches.Then establish a stabilized approachangle and airspeed of not more than1.3 X Vso or less (1.2 X Vso) whilecrossing the approach end of the run-way. The use of power for short fieldlandings is important because it allows

the pilot to adjust the pitch attitude tocontrol airspeed and power to controlthe angle of descent. For conventionallight airplanes the airspeed is controlledwith angle of attack (attitude) and therate of descent is controlled with power(see Diagram 6). Note: In some large,airline, swept-wing, jet type airplanesthe above mentioned technique is re-versed — airspeed is controlled withpower and rate of descent is controlledwith elevators. This method is neededbecause of the clean features of theairplane and the slow response of thejet engine requires the use of the abovementioned technique — the conven-tional technique here would be margi-nal.

Effect of flaps during short field ap-proach must be considered next. Thelowering of flaps will reduce the lift/dragratio. This also results in a reduction ofthe maximum gliding distance — thegreater the flap deflection the greaterthe reduction in maximum gliding dis-tance. With flaps the decrease in glidingdistance is accompanied by an increasein glide angle or a steeper glide path(see Diagram 7).

We mentioned earlier that the samefactors which affect takeoff distancealso affect short field landing distance.The principal factors affecting landingdistance include: 1) Gross weight, 2)Runway Condition, 3) Wind — same ef-fect as noted for takeoff distance, 4) De-nsity Altitude (for each 1000 feet in de-nsity altitude the landing distance willincrease by approximately 3.5 percent),5) Landing Speed — a 10% increaseabove the 1.3 X Vso will cause about a20% increase in landing distance — tryit sometime and it will make you a be-liever. It is important that approachspeeds be at plus/minus 5 knots (1.3 XVso) which is the recommendedairspeed for the approach.

The technique used for a short fieldlanding depends, to a large extent, onwhether or not the approach is over an

THE APPROACH• The approach pattern needs

to be wide enough to allowcontinuous use of powerduring the approach.

• The angle of descent con-trolled by adjusting powerand pitch attitude to main-tain proper descent angleand airspeed.

• Adjust power to control airspeed (power is vari-able).

• Do not change glide slope once final descent isstarted.

• Coordinate pitch and power adjustments.

DIAGRAM 6

SPORT AVIATION 31

THE APPROACH• The approach pattern needs

to be wide enough to allowcontinuous use of powerduring the approach.

• The angle of descent con-trolled by adjusting powerand pitch attitude to main-tain proper descent angleand airspeed.

• Adjust power to control airspeed (power is vari-able).

• Do not change glide slope once final descent isstarted.

• Coordinate pitch and power adjustments.

SAME FLIGHT PATH - FLAPS UP N• NOSE HIGH ATTITUDE• CLOSE TO STALL

• STEEPER FLIGHT PATH• NOSE DOWN ATTITUDE• LOWER AIRSPEED

-FLAPS UP GLIDE DISTANCE -

DIAGRAM 7 EFFECT OF FLAPS ON THE GLIDE

BEST ANGLE OF GLIDE SPEED• AIRSPEED CORRESPONDING TO MAX UD

DIAGRAM ?• EFFECT OF AIRSPEED ON GLIDE DISTANCE

obstacle. Without an obstacle, a short-field landing is easier because a steepglide slope is not required. It would beconsidered poor technique to drag theairplane close to the ground slowly withlots of power and place yourself in asituation where an engine failure couldresult in a landing short of the landingstrip, or a gust which might cause astall.

An approach over obstacles shouldresult in a short-field landing well shortof the normal landing point. On your ap-proach over the obstacle and then overthe fence or numbers, gradually addsome power while raising the nose toprevent touching short of the landingstrip. (A slightly higher than normalnose-up attitude should be maintainedwith sufficient power to keep theairplane in the ground effect until the

specified landing point is reached.) Theairspeed can actually be reduced closeto the power-on stall speed and eventu-ally below the power-off stall airspeedjust prior to touchdown (gusty wind con-ditions will require slightly higherairspeeds during the approach).

Under normal conditions, I havetaught my students to use 1.3 X Vso(FAA 1980) until they are over the fenceand then slowing the airspeed to 1.2 XVso and eventually to power-off stallspeed on landing. Just prior to reachingthe pre-selected landing point, about 2to 3 feet above the ground, close thethrottle, gently but firmly, to ensure alanding at the specified point.

Diagrams 8 and 9 illustrate the propertechniques to use at touchdown andduring the land roll.

Upon touchdown, nosewheel typeairplanes should be held in a "power-offstall" pitch attitude as long as theelevators remain effective (FAA 1980).

Tailwheel type airplanes need to beheld firmly in a three-point attitude. Thiswill provide aerodynamic braking by thewings and flaps (if available). Theaerodynamic braking produced by theflaps may, in some cases, be more ef-fective than the use of wheel brakes.However, remember that the effect ofwheel brakes may be reduced substan-tially so long as the flaps are extended.With the flaps extended while brakingthe result could be a skid causing unduewear on the tires.

A few of the most common problemsin performing a short field landing prop-erly occur in the planning phase, ap-proach and landing portions of theTASK. In the approach the rate of des-cent may be too high (see Diagram 7a),or improper use of controls (overcon-trolling results). One of the major prob-lems on landing results from not main-taining a course along the extendedrunway centerline.

TOUCHDOWN

Full flap landing — lastsegment of approach.Use minimum power.Avoid operating on the"back side of powercurve."

• Touchdown atminimum control-lable airspeed onmain wheels. Usepitch at t i tudewhich results inpower off s ta l Iwhen throttle isclosed.

DIAGRAMS

SAFETY CONSIDERATIONS• Abort if serious error in

judgment exists, or iffield is not safe.

• Always be prepared fora crosswind landing.

• Plan your approachover an obstacle.

• Keep tail low so thatairplane does not noseover.

• Clear obstacle by 50feet (safe margin).

• Stop smoothly withinshortest distance con-sistent with safety.

DIAGRAM 9

32 MAY 1985