DC-7 Tankers in Action (part 2)

Larry found his logs from the day of the fire in the video that I will share with you in a moment. But first, a word on (DC-7) T-66. The pilot-in command of T-66 is Brian Lash. Now it was Brian's day off on the day of the Dixie Gulch Fire, so the pilot of T-66 that day was Gene Teske flying with Rick Langstrom (Brian's co-pilot).

Here are the pertinent entries from Larry's log for Sunday the 13th:

Took 2 loads to the Dixie Gulch Fire-Near the fire from yesterday-Coverage 8 full load twice-Went well with ASM A4- T66 came in from Redmond for 2 loads (Gene Tesko/Rick Langstrom)-Later T10 (Chris Holm) and T05 (Skip) loaded at Medford for fires by Klamath Falls-First T66 had to move out of loading pit-Later T62 had to move (with Medford Air's tug to Ericson ramp))-Fly T62 for 45 minutes total-

Larry provides some more specific information about how he was flying T-62 during the drop shown in the video. But first, I went to pause and spend a little time with some terminology that Larry will be using. Flaps are on the wings of most aircraft, we'll get to them in a little more detail in a minute. BMEP refers to power settings of the engines. In this case, the tachometers on the DC-7 indicate engine rpm. Larry spent a little time the other day providing some more details on these terms as applies to his DC-7, T-62:

As to BMEP, about the best explanation that I can give is that it gives a real-time accurate indication in the cockpit of the horsepower being developed by the engines.

On the DC-7 the tachometers actually indicate the engine rpm. The reduction gears in the engine nosecase reduce the propeller rpm by a factor of 16:9, so the prop turns at a bit over half of the engine RPM. This is partially because the prop tips become supersonic above these reduced speeds and drastically lose efficiency. If my math works, the prop speed on take-off is 1631 rpm with the engine rpm of 2900. This is still a rather impressive 27 revolutions per second for the prop and 48 for the engine.

Wing flaps allow the wing area and camber (curvature) to be altered to make it more efficient for either high or low speed flight. For take-off, the DC-7 uses 20 degrees of flap. The wing flaps extend aft increasing the wing area and deflect downward at a 20 degree angle to increase the camber of the wing.Once the landing gear has been retracted and the airplane has gained enough altitude to safely allow for any settling resulting from the loss of lift, the flaps are fully retracted to allow an increase in speed.

Larry sent along two pictures of T-62, one with the flaps extended and the other with the flaps retracted.

Larry goes on:

With the flaps retracted (to zero degrees) there is slightly less wing area and the wing has less camber which allow for higher speed mainly due to less drag. For landing or the final part of the drop pattern we end up with the flaps fully extended to 50 degrees. This is a high drag position that helps to control the airplane's speed. With the flaps on the DC-7, the first 20 degrees is all lift, 30 degrees is slightly more lift, but with some additional drag. Above 30 degrees any increases in flap angle are mostly drag.

For those of you who are interested in some more specifics on the flaps of the the DC-7, Larry says that

the flaps on the DC-7 are double slotted flaps, but the upper slots on the DC-7 are just airfoil shaped deflectors that are the full span of the flaps, but only have a chord of about a foot. In the picture of a double slotted flap from how stuff works, the slots are larger than the rest of the flap.
Here are two links that Larry sent me to share for those of you who want more information about how flaps work, one is from Wikipedia and the second is from How Stuff Works.

With this as background, Larry continues with how he is flying T-62 during the drop in the video:

I had full flaps (50 degrees) out during the part of the drop pattern that is in the video. At least I have full flaps until the retardant starts coming out at which time we normally retract the flaps to 20 degrees (the take-off setting) and go to climb power which is 175 BMEP and 2400 RPM for the recovery and climb out.

In the final part of the pattern we usually have 2400 RPM set and are throttled back to as low as 100 BMEP, which is the minimum that we can set without driving the engine with the prop instead of the other way around. Normally, in the drop pattern, we start out with 20 flaps and 2400 RPM and 130-140 BMEP in order to stabilize at around 140 kts. On downwind for the drop we'll go to 30 flaps and 130 BMEP and maintain between 130-140 kts.Somewhere around base for the drop we'll go to full flaps and whatever power is required to maintain 130 kts.

When I start dropping the retardant I'll call for Climb Power and Flaps 20. This allows the airplane to accelerate without losing lift too quickly. If I need to make an immediate turn or clear a ridge or both, we'll go to climb power and leave full flaps until we can afford to have the airplane settle a bit with flap retraction. It all depends on the situation at the time.