Used Aircraft Report:

TheCessna310DText and photos

by DON DOWNIE / AOPA 188441

The 1960 Cessna 310D flown for this report has been modified with one-piecewindshield. third passenger window and sleek paint job. Ventral fin (right) adds

yaw stability, and baggage lockers have replaced noisy, troublesomeexhaust augmenters at rear of engine nacelles.

Cessna's 310 series of light twinsestablished a class of high-perform­ance transportation tools, which datesback almost a quarter of a century.

We recently flew N566S, a D modelbuilt in 1960. The airplane is stilI alow-time twin with only 2,800 hourson the airframe, 550 hours on therigh t engine and 380 hours on the left.

Older 310s like 66 Sierra have manythings to offer the prospective pur­chaser of a used light twin. They'rebig and fast enough for most businesschores. They're rugged and have beenaround long enough so that ADs areat a minimum and parts are usuallyavailable. Cockpit visibility is far bet­ter than some later-model twins whosebulbous engine nacelles reduce thepilot's visibility.

Just like any other twin with acruise speed of 222 mph at 5;000 feet,the 310D ha~ a cockpit full of levers,gauges and gadgets. It is not a difficultairplane to fly, but a new 310 pilotshould expect to spend a little timelearning the systems so that he canhandle with confidence almost 21/2

tons (4,830 pounds) of airplane.More than a decade ago, I'd flown

one of tlIe original 310s for a Califor-

56 THE AOPA PILOT I DECEMBER 1978

nia manufacturing company for a fewmonths. Aside from a couple of sortiesto the airplane's spawning grounds inWichita, I hadn't had the occasion tofly a 310 'since then until I climbedinto 66 Sierra witlI Phil Most (AOP A223347) on a hot, smoggy day at thesuper-busy Van Nuys Airport near LosAngeles. Most is a 25,000-hour veteranof this business and is a Western Air­lines DC-I0 captain. He's also an A&Pand does all his own 310D mainte­nance between airline trips-so it wasnot surprising that everything was inworking order on this airplane.

Most is justly proud of his airplane.''I've always been a Cessna enthusiast,and really didn't consider any othertwin. The 310's single-engine ceilinggives some protection, even around tlIemountains of the West," he explained.The 310 had a single-engine serviceceiling of 7,700 feet at a time whenthe contemporary Piper Apache beganwheezing at 5,500 feet on one of its160-hp engines.

Most's D model is by no meansstock; few 1960 airplanes are. Air­frame modifications include a ventralfin, stinger tail, one-piece windshield,vent windows, a third-passenger win-

dow kit and nacelle baggage lockers(which eliminate tlIe original, noisy,exhaust augmenter system). All theseFAA-approved modifications are fromBob Fields' Accessories, Santa Paula,Calif.

In addition, the DC-I0 captain re­cently invested almost $12,000 in newKing avionics and saved 113 poundsby removing heavy, vintage nav/comequipment.

The 260-hp Continental 10-470-Dengines are fuel-injected. The recom­mended technique is to start the leftengine first, because it is closer to tlIebattery, thus affording a lower elec­trical-line loss. Fuel goes into the in­jection system intake ports just as soonas the throttle and mixture controlsare opened and the auxiliary fuelpump is turned on. There's no primingneeded.

Should the auxiliary pump be turnedon for any period of time with theengine stopped, solid. fuel will collec1in the intake manifolds, To avoidflooding, and possibly bending a con­necting rod due to hydraulic lock, itis necessary to wait until this fueldrains away before starting the engine.If you suspect tlIat any amount of raw

•Ir

Basic price $59,950

CESSNA 310D

Range at normal cruise(no reserve)wi aux tanks

Range at economy cruise(no reserve) 1,110 smwi aux tanks 1,440 sm

Service ceiling 21,300 ftSingle-engine service ceiling 7,700 ftStall speed 64 kt (74 mph)Landing distance

(ground roll)Landing over 50 ft

620 ft1,720 ft

825 sm1,070 sm

Specifications(2) Continental

IO-470-D, 260 hp(z) Hartzell 2-blade

constant-speed36 ft

29 ft 7 in9 ft 111/4 in

175 sq ft27.61b/sq ft

53,0371b1,7931b4,830 lb

9.3 lb/hp102 gal

31 gal

24 qt200lb

Propeller

Wing spanLengthHeightWing areaWing loadingPassengers and crewEmpty weightUseful loadGross weightPower loadingFuel capacity (standard)Optional aux tanksOil capacityBaggage capacity

Engine

Performance

Takeoff distance (ground roll) 800 ftTakeoff over 50 ft 1,395 ftRate of climb 1,800 fpmSingle-engine rate of climb 440 fpmMaximum level speed 210 kt

(242 mph)Normal cruise speed (70% 190 kt

power, 8,000 ft) (220 mph)Economy cruise speed 148 kt

( 171 mph)

fuel is in the combustion chamber,pulling the prop through by hand (re­member all the cautions) will precludeengine damage. Early 310s were sus­ceptible to engine fires during floodedstarts.

A walkaround convinces you quicklythat this is a good-sized "light twin."The fuel attendant utilized a short stepladder to ·top off the main tanks (tiptanks are the mains on the 310D).While the 310's span is only 36 feet 9inches-just one foot wider than theSkyhawk-the cabin roof is 7 feet 65/8inches off the ground. A two-step, re­tractable entrance ladder to the rightwingwalk retracts as the gear comesup. Watch how you climb it, though;start up this ladder with your left footand you're "out of sync" when youreach the trailing edge of the wing.

Just like any other twin you can'ttop off the tanks, fill the baggage areas,load every seat and get off the groundwithin legal limits. As equipped, 66Sierra had an empty weight of 3,4231J2pounds. Fill the mains (51 gallonseach) and the two 151/2-gallon auxil­iary tanks, and you have just 600pounds of payload. With three of usaboard, full fuel except for about 15

The Cessna 3100

gallons in the auxiliary tanks, cameragear, and the usual map cases andtiedown equipment, we estimated theweight to be within 30 pounds offull gross.

We fired up and copied the ATIS.The temperature was 94°F, which gaveus a density altitude of 3,300 feet (800feet msl). We taxied to the end of Run­way 16R with 8,000 feet of beautifulrunway ahead. Heavy nosegear steer­ing pressures of earlier 310s were re­duced by changing the steering angleof later models. There was no notice­able buildup in engine temperaturesafter our runup, even though we waitedfor almost five minutes before receiv­ing a nod from the tower.

The time from brakes-off to liftoffwas 26 seconds. Had I elected to ap­ply full power with the brakes on andattempted a short-field takeoff, our ac­celerate-to-95-mph-and-stop distance,according to the book, is 2,390 feetunder standard conditions.

With the wide, 12-foot gear tread,the extra area of the added ventral finand good nosewheel steering, there wasno problem in splitting the centerlineand lifting off easily as the airspeedpassed 95 mph. While minimum con­trol speed is 80 mph, a grossed-out310D "is not suitable for single-engineoperation with gear and flaps extendedand the inoperative propeller wind­milling." In fact, the best single-enginerate-of-climb speed, flaps up, is 111mph, and that's the figure to attain assoon as possible.

Up to 15 degrees of flaps are ap­proved for short-field takeoff. This willreduce the distance to clear a 50-footobstacle by some 13%; but it requiresa liftoff between 65 and 85 mph whereany power loss would result in controldifficulties. If the field was that short,Most and I agreed we would wait fora cold day, a strong headwind, onepilot only and just enough fuel tosafely make the next airport.

The weather around Van Nuys wasjust barely VFR, so we dropped thenose to climb at 120 mph for bettervisibility. A power setting of 24 inchesand 2,475 rpm (70% power) producedan excellent 1,800-fpm rate of climb.Clearing the traffic pattern, we in­creased the airspeed to a 140-mphcruise-climb setting and headed to­ward Santa Barbara.

Level at 4,500 feet, we clocked anindicated 178 mph (198 mph true)with an outside air temperature (OAT)of 75°F and a power setting of 2,450rpm and 24 inches manifold pressure.At this setting, we could expect a rangeof 995 miles with no reserve.

It is interesting to note that low rpmsettings increase duration, but do notmaterially affect range without turbo­charging. For example, a dry-tankrange (in 1960, all performance fig­ures were to zero fuel) is 1,325 milesfor 136 gallons in 6.7 hours at 2,450rpm and 16 inches at 15,000 feet;2,100 rpm under the same conditionswould increase endurance to 8.1 hours,but add only 25 miles to the range.

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Left. Shades of the 60s-here's what

the typical 310D looked like when itwas new. Still classy and quick,well·maintained-and often updated­older 310s offer a means to cut thecost of twin ownership. Above. Panelof 66 Sierra reflects modernizationby owner who replaced original, bulkyavionics equipment with almost$12,000 in new King units and gotthe bonus of a 113·pound weightreduction.

While we were cruising up the coast­line, Most suggested that I remove myfeet from the rudder pedals to see howsingle-engine simulation worked out.He pulled back the right throttle tobelow the normal zero thrust of afeathered propeller. As the nose beganto swing to the right, I rolled in leftaileron to raise the right wing. At about5 degrees wing up, the nose remainedlevel and our speed slowly dissipated,but no perceptible increase in bankwas needed to maintain heading.

continued

The Cessna 3100

Stalls in 66 Sierra are routine for amedium twin. The 310 has a heavydown-spring on the elevator controland the ship will tend to pitch up on astall recovery if all wheel forces havebeen trimmed out. In a clean configura­tion, the nose was high, but not enoughto obstruct visibility when the stallwarner squawked passing through 90mph. There was a pronounced buffet at80 so we relaxed back pressure andadded power. The 310D showed notendency to drop a wing.

With gear down and full flaps, thenose was not quite as high but thestall broke more sharply. We put thenose down and briskly added powerand were right back flying again. Atfull gross weight, gear and flaps down,indicated airspeed at the stall is 74mph. This increases to 77 mph witha 20° bank, 85 mph at 40°, and 105mph with a 60° bank. As with mostproduction aircraft, intentional spinsare not permitted.

Our first landing was at Santa Bar­bara, where two of the runways were 'closed for construction. We werecleared in on 15R, a 4,183-foot runwayheaded toward the ocean. A clean air­plane like the 310 takes considerableslowing down. The book recommendsthat "high altitude let-downs shouldbe initiated as much as an hour beforelanding to permit a gradual rate ofdescent while using enough power tokeep the engines warm."

At 160 mph indicated, you can letout 15 degrees of flaps. The 310D'sflaps are essentially dive brakes andadd no area to the wing as does aFowler flap. The Robertson STOL con­version on the 310 series incorporatesFowler flaps, which increase wing areaas they are extended and add materi­ally to short- and soft-field takeoffs.

Gear-down speed is 140 mph or be­low and a comfortable pattern speedis 120 mph. As you approach high­density traffic areas, you'll again noticethat the low, flat-engine nacelles ofthe 310 minimize blind areas. The Dmodel retains the square tip tanks,7-foot, ll-inch airborne canoes, which

The two 51-gal/on tip tankson the 310D are the mains;with the addition of two

IS-gal/on auxiliary tanks arange of about 1,400 milescan be squeezed out ofthe airplane.

serve as the main fuel tanks. Rakishcanted tanks on later models addedanother 12 inches and made storagein older hangars a bit of a problem.However, the big tip tanks are faraway from the cabin and interfereonly minimally with visibility.

With our main tanks still nearlyfull, we anticipated some sluggishnessin aileron control on final approach.This was not noticeable, and the 310Drolled out on final without addedaileron pressure required. Speed wasdropped to 100 mph on short final, andwe had just a little float during theflare.

It is possible to trim out back pres­sure during the flare but, with nothumb switch on this airplane, Ielected, instead of trimming, to useconsiderable back pressure in the flare.If you end up with excessive nose-uptrim on a twin such as the 310 andmust make a go-around, very heavyforward control pressure is requiredat a time when you're usually other­wise occupied.

We taxied in, shut down and hadlunch overlooking the airport wherewe could watch and talk airplanes.Most was enthusiastic about the STC'dmodifications from Bob Fields. He feltthat the ventral fin, similar to thosefound on later 310 models, added tobasic yaw stability, and that thenacelle baggage lockers generally in­creased utility by adding 120 poundsof baggage capacity behind eachengine. The latter installation requireda complete modification of the exhaustsystem, replacing the rectangular, over­the-wing augmenter exhaust with con­ventional exhaust stacks and cowlflaps. A 1976 AD called for inspectionof any corrosive buildup from the aug­menters. The modification on 66Sierra made this AD inapplicable.

The airplane we flew has a five-seatcabin arrangement. Both pilot seatsadjust horizontally, vertically and tiltback. There is sufficient room in frontof the beefy, carry-through main-sparstructure for long-legged pilots, butextending the front seat aft naturally

cuts into some of the leg room of thosesitting behind.

With the checklist attentiveness ofan airline captain, Most has had aminimum of surprises with his 310.He's never taken off with the cabindoor unlocked-a situation that cancause stabilizer buffet, some nose-downpitch and a slight roll (however, open­ing the door just prior to touchdownis recommended for a ditching or aprecautionary forced landing). Mostdid comment that the DC-lO requiredlighter control input and was easierto land than his 310D. Easily made,smooth touchdowns are not charac­teristic of the airplane.

Departing Santa Barbara, we werecleared from the intersection on Run­way 25L, a seldom-used runway withlittle more than 3,000 feet available.However, the temperature was thendown to 64°F and there was a 10-knotbreeze, so we lifted off well withinlimits.

With half the runways at SantaBarbara closed and Van Nuys coveredwith smog, we headed for the hotdesert at Fox Field (104°F) for a fewfly-by photos.

Departing later, we took a predict­ably long, 29-second, takeoff roll (ele­vation 2,327 feet and density altitude6,000 feet) to break ground. Weclimbed out toward the smog layer,polluted even more by a brush fire,and intercepted the Van Nuys lLS.VFR traffic was plentiful as we fol­lowed an Air Guard C-130 down intothe murk. With a comfortable mini­mum approach speed of 100 mph, wehad to be careful maintaining separa­tion with light trainers in the crowdedpattern.

After taxiing to the hangar in thefar northeast corner of this busy air­port, we pulled back the mixture con­trols and considered the value of anolder twin such as 66 Sierra. Yes, this310D, vintage 1960, is so close in per­formance, comfort and appointmentsto the 1979 models that economicsbecomes a major consideration. PhilMost figures that he has.$47,300 in 66Sierra with 10\l.'-time engines andmostly new avionics. A bare-bonesnew model rolls out of the factorydoor at $133,490, and the 310 II withfactory-installed avionics and popularaccessories is $158,990.

The airline captain had figured thatthe only way he will get his completeinvestment out of this 1960 Cessna310 is to fly it out; but at the rateolder aircraft are appreciating, thismay no longer be the case.

There's a great deal more to flyinga 310 than a set of numbers-whetherit be the original model, the D thatwe've used for this report or the latestproduction version. The 310 configura­tion is essentially a first in its field:the basic design put all fuel outboardof the engines in case of a crash; itincorporated flush riveting back to themain spar; and it put the pilot in aneye-appealing package, which flew aswell as it looked. 0

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