FLIGHT PLANNING 101

Flight Planning: Weight & Balance; SIDS & STARS

 

   WEIGHT & BALANCE:   Proper flight planning is just as important as the flight itself. As Clint Eastwood once said, "A man has to know his limitations." On any checkride, the first part of the oral exam is usually limitations. To find the limitations of your aircraft, you can do a quick google search of the web and find the numbers for just about every airplane ever made. For our example here we are going to fly an American DC-6B from New York to Chicago.

 

 

 

 

Step 1: Understanding Weights

Empty Weight (EW): This is the weight of the airplane when it rolled off the assembly line. 

Basic Operating Weight (BOW): This is empty weight plus pilots, stewardesses, normal catering supplies, unusable fuel and full oil.

Zero Fuel Weight (ZFW): This is the BOW plus any cargo and/or passengers you have. Average passenger weights today are 180 lbs per person, and 25 lbs per checked bag. A large woman with a laptop, carry-on bag, big floppy hat, baby, umbrella, winter coat, is still considered to be 180 lbs.

Ramp Weight (RW): Add your fuel load to the ZFW and you get your ramp weight.

Maximum Takeoff Weight (MTOW): This is ramp weight minus taxi fuel. Generally we consider taxi fuel as the fuel used in ten minutes of taxi. MTOW is the maximum the airplane can weigh at the start of the takeoff roll.

Maximum Landing Weight (MLW): This is the maximum that the airplane can weigh when touching down at the destination. This is often your limiting factor. Take your maximum landing weight (MLW) and add the enroute fuel burn. This is your MTOW for this particular flight.

Weights affect performance. The higher the weight, the higher the speeds needed for takeoff and landing and the longer the runway you need. If you exceed these limitations, then the performance charts are no longer valid and if anything happens, you're cooked! Exceeding a weight limitation puts your license, your livelyhood and your life at risk. So never, ever exceed these limits. Know your limitations!

 

Step 2: Fuel

First of all, start thinking of fuel in terms of pounds, not gallons. Small aircraft buy fuel by the gallon, but large aircraft buy it by the pound. The one question every pilot needs an answer to is "How much fuel do I need?" Without fuel, you're just a falling brick, so we like to have plenty of fuel. You can't just top off the tanks though. There is one pesky limitation that limits almost every transport category airplane (over 12,500 lbs): Max Landing Weight. If you can fill the seats and top the tanks without going over maximum weight, good. But you may have to fly a very long time to burn off enough fuel weight to get down to your maximum landing weight. So we need to know what is the minimum fuel that we need. If there is room for some more, great! But extra fuel means extra weight which hinders performance. So proper fuel planning is an essential part of flight planning overall.

You need to know three things: Climb fuel burn, cruise fuel burn, descent fuel burn. For taxi, I usually use about 100-200 lbs in the DC-6B, three times that in a jet. It's hard to get specific because one day you taxi five minutes and go, while other days you are tenth in line for takeoff. On your next trip, note the fuel at the ramp. Note what it is after a ten minute taxi. Then note what it is when you level off at cruise, when you start your descent and when you land. This will give you a good idea of you airplane's fuel burns.

Climb: My CalClassic DC-6B checklist says to use 39"/2400 rpm for climb. At 500 fpm this will give you about 170 kts with an average of 2640 pounds per hour (PPH). Today I calculate a thirty minute climb to 16,000', 1360 pounds of fuel, covering 85 miles. 

Descent: For descent I only pull the power back a few inches and let the speed build up to near maximum. This works out to about 240 KTAS at 1000 feet per minute. From 16,000' we need 15 minutes to descend. That is about 450 pounds of fuel and 60 miles.

Cruise: In cruise I go with max power/high weight figures, which is 34"/2100 rpm. At 16,000' this equates to 2920 PPH with the mixture properly leaned and 224 KTAS (true airspeed). Long range cruise will give a fuel flow closer to 2000 PPH, with only a ten knot difference in cruise speed. Today we have 654 miles from LGA to Chicago. 654-85-60= 509 miles in cruise. 509/224= 2 hr+15 min.

Totals:

Time: 30 min climb + 15 min descent + 2+15 in cruise = 3 hours total. 

Fuel: 1360 climb + 6570 cruise + 450 descent = 8380 pounds of fuel.   Reserve fuel is 2200 lbs. Fuel to get to our alternate is 3000 lbs. For this flight, we will use 15,000 lbs of fuel as our fuel order.

 

Step 3: The Math

Where I have worked we always had a sheet for weight and fuel calculations. Here is an example of some I printed up for myself to use at home.

First note the BOW, 58,340 lbs. To find this figure for your airplane, go to the aircraft.cfg file in the aircraft folder. Open it with notepad. If you're not used to making changes here, best to not make any at all. Scroll down to the weights section. Here you will see the BOW.

For our flight to Chicago, we will have a full load of passengers, 102 happy souls. At 180 lbs each, that is 18,360 lbs. I added one checked bag per person and that weight is 2550 lbs. Together the make up our load, 20,910 lbs. Add this to the BOW and you get Zero Fuel Weight, 79,250 lbs. This is below the Maximum Zero Fuel Weight of 83,200 lbs, so we are good here.

So we can carry a full load of passengers and less than 50% fuel and we will have enough to get to Chicago, shoot the approach and then divert to St Louis with adequate reserves.

 

ROUTES:

 

Today routes are easier to plan. Originally, you drew a line on a chart, figured the course, corrected for winds, selected checkpoints and wrote it all down. Then as you progressed along your route, you watched for those checkpoints and corrected as needed. This is how early aviation did it. Later the NDB and VOR gave us a means for navigating while in the clouds. An NDB just points to the beacon. A VOR can be set to a specific course and flown accordingly. Then along came GPS and things got really simple.

Step 1. SIDS  

SIDS are Standard Instrument Departures, providing standardized routes from many larger airports. Almost all commercial aircraft fly a SID when departing. If you want to fly a SID, go to AIRNAV.COM or FLTPLAN.COM and look up the airport, then scroll down and select a SID that best matches your direction of flight. On the right is a typical SID, the LaGuardia 7 (LGA7) departure from New York. I'm headed to the west towards Chicago, so I'll select a point in that general direction, like Sparta (SAX). Putting this in the FS flight plan is pretty easy, just make your first point SAX. 

 

 

 

Step 2: STARS

 

STARs are Standard Terminal Arrival Routes. If the airport is busy enough, they'll have a STAR. The smaller the airport, the simplier the STAR. Every STAR has an entry point. Look at the example, the GOSHEN EIGHT arrival. We selected this because we are coming from the east. GOSHEN (GSH) is the entrance point. Think of it as the front door to Chicago. We'll fly this to Chicago Heights (CGT) and turn right to Midway from there.

 

Step 3: ENROUTE

From SAX to GSH is my enroute phase. I can select airways, VOR to VOR, or GPS Direct. If you're at or above 18,000, use High Altitude (Jet) Airways (J41, J319, etc). Below FL180 use Low Altitude (or Victor) Airways (V129, V3, etc). How you fly the enroute phase is up to you. 

 

That's flight planning! We know where we are going, how much we will weigh at takeoff and landing, how much fuel we will need. Enjoy!