Risultati immagini per DC-6B CB16Risultati immagini per DC-6B CB16

 

 

Douglas DC-6B CB16 MiniTutorial

 

(adapted from the DC-7C minitutorial)

 

by FSAviator

 

Real world DC6B target performance at max gross / nil wind / ISA / sea level calls for the aircraft to be 10 metres above the runway 4500 feet after brake release. Few airline pilots would actually have achieved this at every attempt. The updated FS9 FD will deliver that possibility to within the usual error % present in any MSFS flight dynamics which must also deliver many other cases. At 25C and at 2000 feet QNH that distance becomes 5000 feet. Any FS9 flight dynamics are likely to be a little 'long' for one case and a little 'short' for another.

 

Some users may have unrealistic expectations that the take off distance for a DC6B should be less.

 

At max gross with FLAP 2 deployed at around 115 KIAS a DC6B needs a very substantial angle of attack to fly at all. The rotation (at 115 KIAS at max gross) must be very positive, but not excessive.

 

In DC6B terms 115 KIAS is not a lot of airflow. The elevators are not fully effective and a large aft yoke movement is necessary to achieve a large angle of elevator deflection to achieve + 8 pitch quickly. We don't need to be nearly as aggressive when flaring for the landing from a similar IAS because we have full flap deployed and developing much more lift.

 

Once we unstick with very positive rotation the problem is then not lack of climb performance but preventing excessive climb rates. Rate of climb must quickly be restrained to almost nothing until the drag reaches 130 KIAS.

 

****************************

 

Take Off (with water/meth injection):

 

APPLY BRAKES

MIXTURE - AUTO in realism screen

CARB HEAT - COLD

TRIM + 4 degrees 

FLAP = STAGE 2

PROPS = MAX RPM

 

IF ADI/AF desired/required: ADI & AF ON

Invokes water/meth injection giving 59.5" MAP @FT

WET departure/AF is MANDATORY > 92,200lbs

*DRY TAKE OFF SET MAP = 53"

 

COWL FLAPS = 4 degrees

Check CHT < 260C

 

CALL for TOGA POWER  (2400hp WET)

RELEASE BRAKES

Slowly apply FULL THROTTLE or 53" DRY

ROTATE at 115 KIAS   (@ 103800lbs)

Establish positive rate of climb

GEAR UP

 

ACCELERATE > 130 KIAS @ <= 500 ft/min

 

CLIMB 300 feet AGL

FLAP = STAGE 1

 

ACCELERATE 140 KIAS @ <= 500 ft/min

FLAP = UP

 

Establish 500 VSI

CALL for METO Power (1800hp)

 

**********************************

 

Note that we should hold the aircraft below 300 AGL until 130 KIAS is achieved. Climb rate should be very low. This post unstick phase is all about using the only briefly available TOGA power to accelerate the aircraft to the 'right side' of the drag curve as fast as possible. It is not about climbing.

 

Once we have achieved 140 KIAS about 300 feet above the runway elevation we get rid of the drag of the flaps and stop thrashing the engines to death and reduce to METO power.

 

**********************************

 

METO Power (1800hp x 4):

 

48 inches MAP

2600 RPM

160 KIAS

 

ADI & AF OFF

 

COWL FLAPS = 4 degrees

Check CHT < 260C

 

Above all obstacles:

VSI = 500

ACCELERATE > 180 KIAS

 

CALL for climb power

 

***********************************

 

We have just shifted up from first gear to second. All propliners have manual shift gear boxes. One gear shift lever for each airscrew. In an aeroplane we call the gear shift levers rpm levers. In a car with manual shift we need to select first gear for pulling away from the kerb. The engine must be revved hard even at very low speed to get things rolling.

 

Once we are rolling and have developed enough speed we must select second gear. Staying in first gear would be wrong and shifting straight up to third would be wrong. In first the rpm would be too high and in third too low. When we are about to climb a hill in a car we must make the gear ratio (rpm) match both the steepness of the hill and the speed we approach the bottom of the hill. Aeroplanes are no different. We have to shift up (reduce rpm) manually in a piston propliner, as we accelerate, whether or not we are going up hill.

 

In the DC6B first gear = 2800 rpm is great for pulling away from a standing start and getting things rolling, but now we have reached 140 KIAS and we intend to steepen the gradient of the climb to 500 VSI. We must shift up to second gear (2600rpm). We cannot accelerate a car with a manual shift gear box to economical cruising speed in first gear and it doesn't work in aeroplanes either.

 

The principle reason that users of the DC6B fail to climb the hill after take off without stalling is that they try to climb a steep hill at 500 VSI before building up speed to 140 KIAS and also try to do it in the wrong gear. We have to both build up speed and select the correct gear (rpm) before tackling a hill climb. In an aeroplane we choose when and at what speed to tackle a climb. Much of the Propliner Tutorial is about how and when to even try.

 

Once the DC6B is in the correct gear ratio (2600rpm when throttle = 48 inches of MAP) it will accelerate to 160 KIAS even whilst climbing a hill. If we try to tackle a hill that steep with the speed below 150 at the bottom of the hill, or in the wrong gear for that gradient at that entry speed, it just won't make it up the hill.

 

We are now accelerating up hill in second gear (2600rpm at 48 inches). When we get the speed up to 160 second gear is too low even though we have no intention of changing the climb rate from 500 VSI. We shift up to third by selecting 39 inches and 2400rpm.

 

**********************************

 

Climb Power (1400 hp x 4):

 

39 inches MAP

2400 RPM

170 KIAS

 

COWL FLAPS = 4 degrees

Check CHT < 232C

 

IF UNABLE to maintain 500 VSI @ 170 KIAS

(or use Initial Alt value on Notepad)

 

REQUEST LEVEL OFF from ATC

ACCELERATE > 180 KIAS

 

***********************************

 

Each time our increased speed allows us to shift up we reduce the load on the engine (reduce its rpm) and extend its useful life (time between overhauls). Once we are at a really decent speed we can get into gears that allow as to continue acceleration (up hill), with less and less power, burning less and less fuel, so we choose to do just that. High gears (low rpm) are more efficient, but they are incompatible with climbing hills at low speed. We can only shift up as speed increases, but we must shift up (reduce rpm) at the right time and make sure we choose the correct climb rate for the current speed and gear selected.

 

The handling notes explain how steep a climb we can handle, what speed we have to be when we arrive at the bottom, what power we need to supply with the throttles, and what gear we need to select using the rpm levers.

 

After the take off phase is over international law requires us to climb at not less than 500 VSI. If our virtual airline or military employer wants us to climb faster they supply handling notes that explain the throttle and rpm values required for the higher target VSI or they specify constant IAS with varying VSI.

 

Of course when we are ready to cruise (reach operational ceiling) we shift up again from third to fourth.

 

***********************************

 

High Weight/Speed Cruise  (1100hp x 4):

 

>89,000 lbs: High Wt. Econ Cruise

<89,000 lbs: High Speed Cruise

UAL Standard Cruise Power

 

MAP = 34 inches

RPM = 2100

 

****************************

 

In a DC6B we just shift up (reduce to 2100 rpm). When we are running lighter we take the opportunity to shift up to fifth (overdrive = 1850rpm).

 

****************************

 

Econ Cruise (1000hp x 4):

 

Use only <= 89,000lbs

 

MAP = 32 inches

RPM = 1850

 

****************************

 

Just don't try climbing steep hills from a low speed at the bottom in overdrive. When we hit the built up area and the traffic near our destination we need to slow down and shift down again (to higher rpm).

 

****************************

 

Approach and Circuit:

 

Cross FAF = 140 KIAS & FLAP 2 deployed

 

2400 RPM

MAP => 24 inches

COWL FLAPS = 2 degrees

 

***************************

 

If we need to go around we must select full throttle and first gear because we will be about to climb a steep hill from very low speed,

 

***************************

 

Baulked Landing:

 

CALL for EMERGENCY POWER

PROPS FULL FINE

FULL THROTTLE

 

***************************

 

Maybe this is all more apparent to Europeans who nearly always drive cars with manual shift, but I suspect that failure to climb the DC6B without much difficulty is the result of not fully understanding the above even though it was always promulgated in the handling notes.

 

Although not strictly relevant at this point note that the flight planning fuel flow values in the DC6B handling notes are per engine which is anomalous compared to my other handling notes which promulgate the total for all engines.

 

Finally Part 4 of the Propliner Tutorial explains how to make the departure phase more realistic and uses the Sebago departure from KIZG as the worked example. That worked example in the tutorial talks about the DC7B rather than the DC6B so I have abridged it here with specific relevance to the DC6B.

 

 

Climb Stage 1 is for obstacle clearance. The obstacle can be a mountain, a mast, a gunnery range, another airfield's holding pattern, a nature reserve, or just noise abatement at a sensitive site such as a hospital. The departure procedures for the runway will not usually tell us why we must proceed to a given fix after take off and cross that fix at a minimum altitude, but we must.

 

When we receive, (issue to ourselves), the realistic ATC clearance, 'cross Sebago 3500 or above' we must bear in mind that Sebago is a fixed distance from KIZG. Climb rate is unimportant. We must instead target a good climb gradient. We achieve a better climb gradient (per mile) by restricting IAS even if we climb at the same rate (per minute).

 

Remember this is just an example. A DC6B would need to be very light and have a favourable headwind to depart KIZG at all.

 

The DC6B handling notes cannot cover the details of all real departure procedures everywhere. We have to adapt them to each specific case during flight planning. In this case we will not terminate stage 1 climb until we have complied with the realistic local clearance 'cross Sebago (at an ALTITUDE of) 3500 QNH or above'. We will substitute this specific local restriction for the generic handling note noise abatement restriction which is climb 2000 feet QFE (agl).

 

 

**********************************

 

METO Power (1800hp x 4):

 

48 inches MAP

2600 RPM

160 KIAS

 

ADI & AF OFF

 

COWL FLAPS = 4 degrees

Check CHT < 260C

 

Above all obstacles:

VSI = 500

ACCELERATE > 175 KIAS

 

CALL for climb power

 

***********************************

 

Departing KIZG in a DC6B we will climb in METO power towards Sebago at 160 KIAS until passing 3500 QNH. The generic requirements of the handling notes must be translated into the specific requirements of the departure phase from each particular runway. We will not begin acceleration to 175 KIAS until we have achieved the cross above restriction of the departure clearance and we will not exit METO power until we have achieved our final stage 1 climb operating target of 175 KIAS, which we only attempt after clearing all obstacles.

 

Or to put it the other way round. We must climb at only 160 KIAS (Vx), using exactly METO power = 48/2600, achieving much more than 500 VSI, until we are clear of all obstacles, but once we are clear of all obstacles we will accelerate to 175 KIAS (Vy) at only 500 VSI. Only when we have achieved 175 KIAS at 500 VSI can we proceed to climb stage 2.

 

During each departure we decide when we are clear of all obstacles, ideally using the real airfield departure procedure downloaded from the web site of the real federal authority, else we must decide what altitude is adequate by other means and on passing the altitude we decided upon in our flight plan begin acceleration from Vx (best climb gradient) to Vy (normal climb).

 

If that is not making much sense or you are thinking of obstacles as things the size of trees and buildings near the runway try departing Los Angeles eastbound and turn direct for New York in good visibility. Those mountains are the obstacles to be avoided during this departure. Handling notes are not a check list. They explain the targets to be achieved and the captaincy decisions to be made. If we do not download the real procedures with the real departure route and the real cross above restrictions we must determine by visual reference to the surface when it is safe to exit stage 1 climb airframe configuration, IAS, MAP and rpm criteria and begin stage 2 climb. Just like cruising level the correct solution varies day by day, even on the same route, towards the same obstacles, at the same weight, because it varies with the weather, especially headwind vector.

 

The handling notes for the DC6B have always reflected the fact that it has a poor post take off climb gradient at Vy = 170 KIAS and it has to target a lower IAS = Vx = 160 until all obstables have been cleared.

 

The phase by phase on screen handling notes tell us the targets which we must achieve one at a time, in exactly the sequence specified, before we can move to the next phase of the flight. Doing things in a different sequence is not an option. Moving on without achieving all the targets is not an option. The exception is transition from climb to cruise.

 

In general when we cannot sustain 500 VSI at constant Vy using the correct throttle and rpm setting for the correct and current climb phase we have reached operational ceiling and must transition to cruise. As I have explained in another thread that would normally be triggered by less than 500 fpm at 160 KIAS in a DC6B. We may also need to exit climb for cruise if max specified engine temperatures are reached during climb.

 

Big complex aeroplanes are designed to be flown by the numbers. The input numbers such as Trim %, FLAP stage, MAP and rpm and the output targets such as IAS and VSI. Hit all the numbers in the correct sequence and they handle nicely. Miss them, or even achieve them in the wrong order, and they may handle like pigs.

 

 

FSAviator 12/06