dc3throt

2. The cylinder head temp. probes are not able to give a true picture of heat extremes during take-off. (the extra enrichment supplied by full throttle -max power results in substantially lower CH temperatures).

Rob Campbell says.... One other 'thing' about the procedures in regard to using power. We NEVER reduce the MP below the RPM until the final reduction as the landing is assured. To reduce the power earlier invites the propeller to drive the engine and starve the main bearings of oil - this regardless of the speed of the aircraft - but especially if the speed is higher. If there is any question about this, the next time you fly, put the props full forward on downwind or at the outer marker, hold 100 kts and pull the power off to get down - you can actually hear the lugging of the engines. Proper use of the flaps w/ a MP setting no lower than the RPM will allow for a very nice descent rate.

The DC-3 with a single stage blower can stagger up to 14 or 15,000 ft. The hot days at high altitude fields are a problem. The airport might have less runway than the distance required for takeoff. The trick is to get airborne early in the morning when the air is cooler.

A rule of thumb for power loss is 1" of manifold pressure (and therefore atmospheric pressure) per 1,000 ft. A normally aspirated engine can deliver about 30" of manifold pressure at sea level. At a 5,000 ft asl airport, only 25" would be available, so you have thinner air and less power available. At 5,000 ft. the DC-3 can pull 47.5" for takeoff, but that's it, the throttles are at the stops.

DC-3s aren't unique here, all aircraft are affected by density altitude. When you read about some Cessna crashing on takeoff at Lake Tahoe on a hot day, you can bet the pilot was a flat-lander who took the family to see the big lake in the mountains and then wanted to get home before dark. So he takes off at the hottest part of the day when the heat gives the 5,000 ft asl field a density altitude of 8,000 ft. As he is crawling down the runway, he travels the distance that he normally does at sea level and pulls back on the wheel, the aircraft stalls, falls off into the start of a spin and crashes by the side of the runway. Fortunately, more attention is given to high altitude airports and density altitude now during primary instruction. However, all the instruction in the world is no substitute for the experience of performing a takeoff at a high altitude field on a hot day.

The acceleration during the takeoff roll is very slow; the take off distance is very long; it seems to take forever for the airspeed indicator to reach the number required for liftoff, and, once you get airborne, the climb performance is truly anemic. The trick is to be patient and watch your airspeed. The same indicated airspeeds are required.

Another rule of thumb (with Wright engines) was to use about 21" and 100 knots as a "baseline" then add one inch MP for every 10 knots above that. Works out about the way your rule does. Just to put the concept of "backload" as you call it, in automotive terms, I think about being established in cruise and downshifting a gear at a time as with a manual transmission used to help slow down the car. Just as you would not want your car to be travelling down HWY 101 at 65 then abruptly downshifting into first without first decelerating significantly (makes more sense to downshift slowly through 4th, 3rd, 2nd as one bleeds off speed-- and energy).

After using full rated takeoff and climb power, if you're not in a hurry (and who in a DC 3 is in a hurry?) use 27" or 28" and 2150 rpm in cruise.

What about descent and approach to landing? This is a flight regime in which much damage can be inflicted on the engines by reducing power too quickly.

Most round engine drivers and those who have a great interest in the old birds have heard the term "backlash" or "backloading". It refers to the prop driving the engine. This can occur in a descent at low power settings. When the prop drives the engine, all the forces on the bearings and gearbox are reversed, and this is what causes the damage. The bearing surfaces and the gearbox are not designed for these opposite pressures.

So...to keep the engine driving the prop, here are some airspeed guidelines. Above 140 kts. IAS...keep at least a 5" spread (ex. 2150 rpm / 26.5" map); 100 to 140 kts., at least square (ex. 2150 rpm / 21.5" map). Manifold pressure should not be allowed to go below the corresponding rpm until the airspeed is below 100 kts.

Another guideline on power reduction is no more than 2 inches every 2 minutes. This assures gradual cooling.

Another good practice is to make all power changes very slowly. The old gauges take a while to register the new power settings, and there are a lot of moving parts in the engines which need time to adjust.

The term I learned back in the 70s when I started flying 3s was "backloading". In addition to starving the bearings, the loads on the bearings are reversed. The master rod bearing is the one most prone to damage. Also the loads on the prop reduction gears are reversed. All it takes is one incident to ruin an engine.

Flying night cargo and fitting into LAX traffic with the jet freighters, we got real creative on flying fast approaches 150 kts. at the OM was not uncommon. Gear down at 150 to 160 kts., then 1/4 flaps at 130, and judicious reduction of MAP and RPM together to avoid backloading. With 11,000 feet of runway, we'd cross the fence at 100 kts, then go to full flaps, land and turn off at mid field.

One has to adapt to the modern world. It's great that the DC 3 is so adaptable.

I would like to say that using the brakes while the tail is up will result in a nose over is a myth- if done properly. As a new copilot, I watched the Captain land in a level attitude with the throttles closed, apply full brake effort and keep the pitch steady with alot of up elevator. As the brakes heated up (expander tubes, I do not know how the drum or disks behave) they faded. This resulted in a 1500' ground roll with weight around 24000#. I was not so brave, and would wait until the tail was down to put the brakes on, but still held aft yoke to keep the tailwheel on the ground. Several years later I was involved in writing an Airplane Operating Manual for a new DC-3 Air Carrier Certificate, and researched several other operators manuals, AFM's, and millitary tech orders. Somewhere in the hunt, I found a statement that full brakes could be applied at speeds above 40 knots, below which the elevators may not be able to prevent a noseover. Makes sense to me, I flew with another Captain that stood a DC-3 up on the mains on a taxiway after applying brakes too hard with a tailwind. In my own experience as a company instructor for a freight operator, I have demonstrated that brakes are more effective with the tail up and flaps up. If heavy braking is used immediately after touchdown on the mains with the tail low or on the ground, the wing is at a large angle of attack and producing some, albeit not much, lift and the tires will skid. Conversely, holding a level pitch puts all of the weight on the mains, and reduces angle of attack so very little lift is produced by the wing, and the brakes can be held to the floor with lots of up elevator and a short ground roll made. I teach my pilots to either have the tail up or down during rollout. Up gives rudder effectiveness, down lets the tailwheel help with directional control. It is when the tail is just barely off of the runway that all of the "fun" happens if the brakes are uneven or if a gust of wind comes along. DISCLAIMER ABOUT BRAKES: Each plane I have flown has had a different sensitivity to the brakes and yours might tend to noseover if pedals are held all of the way down! I have only used expander tube brakes. About three pointers: I think they are fun to do on a calm day or night with an empty airplane, but if flare height is wrong it will be a big BOUNCE or a hard DROP. The main reason I do not do them more than a few times a year, or permit my FO's to do it is that a go-around might be difficult to safely accomplish. Unless you are very strong, slowing down for the landing requires nose up trim to the degree that a go-around would be a quick stall entry. Since stall speed is so low, we are also way below VMC, and directional control would be a hand (foot) full if the engines don't both come up to power equally. Finally, crosswinds add just that much more work. I have held full rudder and lots of aileron to keep it going straight down the centerline. Apart from all of the bad, it feels pretty neat to feel the plane land as the elevator reaches the aft stop, and looks cool to be so high going so slow in the flare. I use the same power settings as you do with -92 and -90D engines and have had good luck. We do not go below 20" without reducing RPM at any time except for roundout and flare. Have you noticed how quiet it is at 1700RPM in flight?

Buzz Meyer who is restoring a DC-3 in the livery of Eastern Airlines to flying condition had this to say..... In Short, operating costs are approximately $450 to $550 per hour, depending on what you set aside for engine and airframe overhaul. You would burn 90-100 gallons of fuel per hour, and 2 gallons of oil per hour. A DC-3 is about the least expensive large airplane that a couple guys can afford to work with. Parts are generally available. Skilled DC-3 mechanics are getting rare, and DC-3 pilots can still be trained at about $650 per hour for lessons.

If you use brakes in a DC-3 whilst the tail wheel is still in the air (usually after a main wheel landing), the chances are, your DC-3 will nose over. I have seen some pictures of a Delta Airlines DC-3 at Chicago's Midway Airport where this happened. A Crane had to be brought in to right the DC-3 onto it's wheels again.

I once heard a story that some of the more experienced C-47 pilots were able to bring a DC-3 to a complete stop after a main wheel landing and BEFORE the tail wheel had touched the runway.

4=Adjust Power as Desired: Normal Cruise - MP 32" 2000 RPM, Economy Cruise - MP 31" 1850 RPM

These figures are for Wright Cyclone GR-1820G-202A engines with 3:2 reduction gearing, but apply to most Wright engine types on DC-3's. Also of note, is that the throttle quadrant on a Wright Cyclone engine DC-3 is different, in that the Mixture controls are placed were the carb heat controls are on a normal DC-3 and the carb heat throttle controls are placed were the Mixture controls usually are. See the Delta Ship 41 DC-3 cockpit picture below for an example of this unusual throttle quadrant arrangement within the cockpit photo. A Wright Cyclone engine has a single bank of 9 cyclinders unlike the 2 banks of seven cylinders on a typical DC-3. Also, spares for Wright engined DC-3's are extremely rare to get, making maintenance on these types very difficult.

The excellent restored cockpit of Delta Air Lines "Ship 41" a Wright powered DC-3

A further power reduction can be made for long-range cruise using 37.3 in' MP with props at 2300rpm with 1000hp.

The following specs on the SC47 might be of interest to you. Max allowable TO weight was increased to 32500 lbs. In order to give the desired range for a mission, fuel configuration included 4 x 200 gallon tanks in the fuselage. In the early months of 1956, a modification included the installation of elongated elliptical fuel cells in the wings--400 gallons each. The fuselage tanks were removed. Mission requirements for landing over an obstacle and restricted to a 1200 foot landing strip, necessitated that approaches be fairly steep, full flaps, a little above stall speed. The objective was to cut power off with a full stall, three point landing at touchdown, holding the stick back while applying full brakes--hard--for a few seconds. The tail would come up and then lower as back pressure was released. The only modification to the gear was the installation of a steel drag link. For TOs, we would set flaps, hold the brakes, apply full power briefly then release. You would hit the JATO button at 45 mph. The JATO lasted for 15 seconds, but you had pretty good speed and altitude (obstacle criteria) by then. The original unit was activated by SAC to provide recovery for downed aircrews. Low level flying tactics were part of the training for the unit. See this 45 year old picture of a SC-47 below.

Robert Moninger says.. Speaking of icing, the DC-3 let you know when you were in icing conditions. De-icing fluid (ethylene glycol) was applied to the props through slinger rings, and fair sized chunks of ice were thrown against the fuselage, which was re-enforced in the arc line of the props. The decibel level created quite a disturbance for both the passengers and, I must admit, the crew, varying in proportion to the intensity and duration of the icing condition. Other disturbing items: the wind-shield would accumulate a coating which could only be removed by (A) flying into warmer air (seldom happened) or (B) sliding open the side window and scraping it off with a putty-knife, stored in a leather scabbard on the bulkhead, behind the captain's head, not a pleasant chore In addition, airspeed would steadily decrease as the ice accumulated, sometimes to the point where altitude could no longer be maintained. To make it more exciting, chunks of ice would occasionally break off the cowling and find their way into the carburetor intakes, resulting in spasms of coughing and sputtering --- and that included the engines.

In late 1942 United contracted with the Air Transport Command for two areas of operation, to Alaska using C-47s, and to Australia, using C-87s. The Army Air Corps supplied the airplanes, United supplied the pilots and operating personnel. We were issued uniforms similar to those of the Army Air Corps but with unique insignia that no one in the U.S. military forces had ever seen before. This led to complete confusion as to who should initiate the saluting process. As we were essentially civilians, we weren't too proficient at saluting anyhow, so there were many awkward encounters.at the military airfields. I was assigned to the Australian operation but heard many tales of the indomitable C-47s and the crews who maintained a remarkable percentage of their schedule in some of the worst weather you can find anywhere in the world.

June,1943 - upgraded to Captain and was sent to Denver where United was operating a school for the Army Air Corps to transition cadets from single to multi- engine airplanes. We instructed around the clock flying C-49s, which were powered with Wright Cyclones and C-73s, which were P&W equipped. I personally much preferred the P&Ws. Four other United guys and I rented a large house in central Denver and since we were scheduled at all hours we needed an alarm clock. Augie Heldt was the only one among us with one, the problem being it was somewhat eccentric. It was an old "Big Ben" and gained ten minutes every hour and the alarm sounded six hours after the time the alarm was set for. Augie was the only one who could program it to go off at the desired time but it worked surprisingly well. We usually flew two sessions a day , two cadets at a time , 2 hours + per session. Since we weren't too closely supervised we managed to squeeze in some low level cross country , giving some farmers their first close-up of a gooney bird. One of our intrepid instructors, under guise of a cross -country to Colorado Springs added a little extra with a side trip UNDER the Royal Gorge Bridge. Only those who have seen this bridge can really appreciate this.

October 1943 - progressed to domestic MATS (Military Air Transport Service). We flew C-49s and C-47s to military air bases in the U.S. I was stationed in San Francisco and flew from there to Denver on a scheduled basis with stops at Sacramento and Ogden, Utah. The airplanes were G.I., the uniforms United Airlines, no funny insignia, no saluting. Next step, in April 1944, was to UAL cargo, flown in UAL cargo DC-3s with a big cargo door on the left side. All of our passenger DC-3s had the door on the right side although most other airlines had it on the left. I have never been able to learn why. Finally started flying passengers in the fall of 1944 and for the next and last year of the war, when flying was still on a priority basis has the privilege of carrying Jimmy Stewart, Eleanor Roosevelt, Bob Hope, Jimmy Doolittle and other well known people.

Warbirds Notes Index

Randy L. Sohn can be reached via E-Mail at Ndper@aol.com

R. L. Sohn � ____________________________________________________________________

#1 HYDRAULIC LOCK ON ROUND ENGINES.....(21 Mar 93)

#2 DECELERATING APPROACH.....(3 Aug 93)

#3 reciprocating load (MP Vs RPM).....(2 Mar 94)

#4 MIXTURE MISCUES & MIXUPS.....(3 Apr 95)

#5 FEATHER BUTTONS & PROPELLERS.....(31 Oct 94)

#6 GAUGE INDICATIONS ON A FAILED ENGINE.....(30 Dec 94)

#7 PRE-IGNITION Vs DETONATION.....(4 Nov 94)

#8 FIELD BAROMETRIC POWER CHECK.....(16 Feb 95

#9 HYDRAULIC LOCK - - - REVISITED.....(27 Feb 95)