Sounds good.  Do you know of any online reference materials that can be used for this?  If you don't, I can scan some performance pages from my PIM for the 172 that could be used.  It should be pretty close to the values we get in the sim.

I was going to use the one of the airplane in the tree behind the learn to fly sign, but decided against it.


Here are a few links that might be helpful for flight planning:

Online Aviation Charts - http://skyvector.com/

Airport information - http://www.airnav.com/airports/

Online E6B - http://www.csgnetwork.com/e6bcalc.html

Weather - http://adds.aviationweather.noaa.gov/

FAA Flight Plan Form - http://forms.faa.gov/forms/faa7233-1.pdf

I changed my sig so maybe a few more people will get interested in this too.

We'll get into more accurate and advanced performance data for the C172 later. For the purposes of Sim training, all we need to know is fuel consumption under normal cruise settings (2400rpm, properly leaned, 9gph at a typical cruising altitude of 4500msl)... and we'll know that 3 gallons will be used for start-up/taxi/takeoff/climb. The MSFS C172's  maximum gross takeoff weight is 2550lbs, and the empty weight is 1650lbs... leaving us 900lbs for fuel and payload.

This demo flight plan will be for a 200lb pilot, and two, 200lb passengers carrying 150lbs of baggage and gear between the three of them... 750 pounds total. Actual loading and CG calculations aren't required for simming. It's an involved process we'll surely get around to talking about, at some point.

Our flight will be from Columbus, Ohio (KOSU), to Mackinac Island, MI (KMCD).

Using the airport distance calculator at AirNav (or the sim's flight planner, or any method you choose), we'll see that a straight-line flight is 354nm. The C172 can be counted on to maintain a zero-wind ground-speed of no more than 100knots (it can fly faster than that, but we have to allow for our inability to hold a perfectly straight track). So, ideally we could cover that 354nm in a little over 3.5 hours. Burning 9gph, that's 32 gallons (always round to the safe side). Add 3 gallons for, startup/taxi/takeoff/climb, and for a VFR reserve of 30 minutes, we'll add another 5 gallons, bringing the total up to 40 gallons.

For flight-planning, Avgas weighs 6lbs/gal...giving us 240lbs of fuel for this trip. We have a passenger baggage load of 750lbs. The total load would be 990lbs; 90lbs over MGTW, so this will have to be a two-leg trip. Even if our winds aloft planning indicates a tail-wind.. you just don't count on that, or you'll end up between possible fuel stops, running low on fuel...

Now.. on to weather planning (next post).

Brett_Henderson wrote on Nov 15^th, 2007 at 11:10am:


Just a quick one Brett, as I've never flown in the states (hopefully not for too much longer); looking at those TAFs, 10SM, 9SM etc - I take it that is met vis in Statute Miles (SM)?...

...I only ask as in TAFs over here it is quoted in Km (5Km and above) or metres (4999m and below) - but is always written in X000 (m)...

Brett_Henderson wrote on Nov 15^th, 2007 at 2:29pm:


Quite! Seeing "SM" though immediately struck me as being odd to my (European) eye...

The next step is to choose our planned fuel stop. Somewhere well past the 1/2-way point will work nicely. Since I've taken this flight for real, many times, we'll use my favorite stop;  Mount Pleasant, MI (KMOP).

Using a VFR sectional, or the sim's planner, or whatever method works best for you... you'll find:

KOSU to KMOP is a true course of 341, and a distance of 226nm.

KMOP to KMCD is a true course of 002, and a distance of 135nm.

Here's a quick look at the flight legs and the wind..




We'll use a cruising speed of 105kias which yields about 107ktas. The indicated airspeed (kias) is lower than the true airspeed (ktas) for reasons similar to how density altitude affects performance. The thinner air at higher altitudes registers less of an effect on the pitot tube, hence a lower reading on the airspeed indicator. Homework for all you aspiring sim pilots is to learn how to come up with true airspeed (which includes the calculated airspeed, but in C172's at low altitude, we'll consider true and calculated airspeed to be one in the same). In zero wind, true airspeed and ground speed are identical.

OK... using an E6B (or online emulator)(or any version of vector analysis that you like) we'll now determine how the wind will change our heading and ground speed. I used the link that Mobius graciously provided to plan the first leg.....




You can see how the wind alters the heading we'll fly, and how the ground speed is affected.

Next we need to convert the TRUE course/heading to MAGNETIC, since all flying, navigating and runway numbering is by magnetic compass readings. The difference between true and magnetic north is not a constant. It differs by location. For a flight of this length, a quick check of a VFR sectional (you can see this at the Skyvector website too) at a point near the middle of our flight shows a magnetic line of declination (the variance) of , "6*W" ...  meaning we add 6 degrees to all our course headings.





Taking our heading adjusted for wind and adding 6 degrees, we get 342 as the compass heading we'll need to fly, in order to track direct to KMOP... and we know that our ground speed will be 73knots.

226nm divided by 73knots means this leg will take 3.1 hours.  3.1 hours burning 9gph = 28gallons... adding 3gallons for startup/taxi/takeoff/climb.... and 5gallons for a 0.5 hour VFR reserve tells us that we'll need a bare minimum of 36gallons to fly the first leg. Double checking our weight (750lbs of people and baggage + 216lbs of fuel (6lbs/gallon)) we see a big,  UH OH ! ...  Because we're STILL over the MGTW  by 66lbs (900lbs of useful load).

I'll leave this discussion open now, for some unofficial and "off the record" talk about what to do next. If someone would like to take the time to calculate a different fuel stop, that would be great. Another opinion or method shared is what this is all about ..

You're getting a little ahead of me and applying a more "real world" approach to this, but that's a good thing. Eventually I was going to point out that this regiment of flight planning is mostly a student pilot thing. There is no pilot alive who can hold a heading +/- a few degrees for more than a few nautical miles... and no winds aloft forecast is accurate enough in either it's direction, or velocity to justify exact calculations.

I'm reminded of my first oral exam. The examiner posed a runway and wind (runway 27.. wind 235@25knots) and asked me to tell him the crosswind component. I couldn't for the life of me find the conversion chart.. so I said.. "If the wind were exactly 1/2-way between pure crosswind and runway heading (225), the crosswind component would be slightly more than 1/2...  since 235 is less than 1/2-way toward a pure crosswind, the crosswind component would be about 1/2 the wind.. or, 13knots, give or take"...

The reason students are drilled like this, is to nail home the whole concept of how wind affects both heading and ground speed. To some new pilots, it's a completely foreign concept. Methods like yours, or even an experienced pilot's mental estimates are accurate enough, so long as you're not pushing the limits (like I have for the first leg). I could glance at a flight plan like this and know right away that that first leg would be in the neighborhood of 3 hours, and at the limit for the C172 as we have it loaded...

I'd still like to see a few alternate fuel stops posted with reasonable estimates for the fuel required... 

Hey !  Where's YOUR alternate fuel stop ?        Grab a sectional whip one up  


Yeah... I'm just trying to get a feel for this.. The discussion started in the FSX forum, and the idea was well received. If it needs to be moved, I'll let the Mods decide...

beaky wrote on Nov 16^th, 2007 at 3:10pm:

Now, now Sean - not all of us are able to cook our own dinner & watch the entire Godfather Trilogy during our flights......  



The lessons look excellent thus far Brett, I'll be keeping tabs & learning myself.



TSC.

I think the theory behind VFR-only weather planning for the sim is covered well enough. I'm still looking for a few, different fuel-stops to show up here.. maybe even another flight or two. I think this will work best, and flow best, if I just keep forging ahead. All this stuff will be here for anyone who comes along and chooses to join in...


OK.. we're grasping the theories about loading.. how that limits the fuel we can carry.. and how wind has the last say in how far that fuel will get us. Again.. all we're trying to accomplish here, is to get people to approach a sim-session, as though it were a real flight. You're whole frame of mind is different when a solid flight-plan in front of you, and sliding that throttle to takeoff power is a little more fun and exciting, when you're thinking like a pilot... Knowing that you have to get, and stay on course keeps you on your toes... and knowing that monitoring you progress is important (it's fun to pinpoint your location by nav-aid, enroute), keeps you "into it".

Now.. the next most important part of this flight-plan, is to be familiar with all the airports where you might be landing. You already know the prevailing winds.. so if you know the available runways, their traffic patterns and the field elevation... the task of approaching the airport is half-way done. All this imformation can be found at www.airnav.com.

Even though our fuel stop at KMOP is out of range.. we'll use it for reference:

Runways are  09/27 ... Field elevation is 755msl  ... Trafic pattern is left hand, for both runways...
AWOS is 110.60 ...  CTAF is  123.00  ...

With all this data at hand, getting from cruise altitude down to the fuel pump (and snack machines (and bathroom)) is just a matter of knowing how to land an airplane..  

Pattern entry (and it's lively discussion) will be covered later; we're still planning.

One last item to cover in sim planning; is to get all the frequencies for the VORs and NDBs that will come in handy as we grope our way from airport to airport (GPS is off limits, for now).

There is one thing that I've yet to mention. We'll pass through or near a couple of controlled airport airspaces (Toledo's class Charlie, and Detroit's class Bravo). For simming purposes, and that we're not into advanced navigation yet, leaves that topic better touched on, later.

As soon as some of you decide to start contributing (wink, wink, nudge, nudge) we can discuss which VORs and NDBs we'd use on this flight, and how, and why..  Other than that, we'll leave advanced navigation until later.

Brett_Henderson wrote on Nov 16^th, 2007 at 7:15pm:

LOL! If I'm the best tailwheel instructor this school has, we're in trouble...

OK, here goes my plan with an alternate fuel stop:

Mission statement: One 200lb pilot, and two, 200lb passengers carrying 150lbs of baggage and gear between the three of them. Flying from Columbus, Ohio (KOSU), to Mackinac Island, MI (KMCD).

Confirmed VFR with winds out of 325 @ 35knots. Air density is a sim standard 29.92

Fuel stop will be KFNT Bishop International AirportFlint, Michigan, USA.

KOSU -> KFNT = 176nm @ 355 (direct)
KFNT -> KMCD = 178nm @ 353 (direct)
Total distance = 354nm

Ground Speed works out the same for each leg, as follows (although the direction will be slightly different):


Wind correction leaves a groundspeed of 75, burning 9gph we will need:

First leg:

176nm @ 75 = 2hrs 35min

Fuel required = 21.5 gallons plus 3 gallons for start up etc (147lbs which leaves 3lbs (1/2gall) reserve - not 5 gall).


I'll stop my planning here Brett, because I have a question, looking at the numbers  (The second leg yields almost identical numbers), it looks like 750lbs in the 172 is not possible (given the winds) to cover 354nm with only one stop - it can be achieved, but only by eating dangerously into our reserve fuel.

Or have I got my calculations wrong?

I'll have to replan incorporating two stops I think.

Cheers,

TSC.

A side note on this flight from actual experience. When you do try to squeeze maximum range out of your available fuel... you end up probing around for an altitude with less headwind.. your track becomes less straight and effficient... you burn more fuel in the climbs... you end up  IN your reserve .... you have to slow down and lean the engine on the hot side... and your passengers don't like the look on your face when you keep re-starting the timer, looking at your watch and fiddling with the throttle and mixture   

Universal, Morse Code translation for any fuel gauge taps...   "find an airport NOW"  

Brett_Henderson wrote on Nov 17^th, 2007 at 12:40pm:

That's because you're trying to do it with the SP, which has fuel injection and leather but doesn't have legs like the older ones. 

Take  the 1969 K model I used to fly: 1000-lb useful load , capable of trimming out at gross for almost 120 kts at typical altitudes...and the O-320 would do this at about 9 gph. You could do this trip at 120 kts TAS with one stop  in an M with 38 gals. usable fuel, even if the average groundspeed was 75 kts...
If you were feeling lucky, you could probably do it nonstop, maybe with an engine-out descent from cruise for a straight-in...

At 5000 and 2500 rpm, it could give you almost 5.5 hours at about 105 knots... so maybe, even with that wind, you could do it nonstop with a healthy reserve.

Sorry; I'm at it again... it's my prejudice against the newfangled Skyhawks, I guess. I promise I'll look at this flight plan later and offer something based on the SP, despite the fact that it has about 50 lbs worth of extra hardware on it just for the extra fuel sample points...

As promised, this should be all the performance data needed from the Pilot's Information Manual for the 1979 Cessna 172N Skyhawk:

Perf. Data File

The data is all in PDF form, and should be relatively self-explanatory, however, in the next couple days I will do a quick run-through of each chart and table and go over how to do a weight and balance calculation and performance calculations.

Also, here is an example of a Navigation Log that you would use to write all the information you need for a flight.  I can go over this in the next couple of days also, but this is what most of this flight planning is for.

Yeah, after I spent so much time on it, I actually wanted to fly it, but it was for my IR checkride, so we didn't get all the way there.

Might be useful to put this in a separate forum section...

Basicall... we're talkin GA here right?

If any of you guys need hints on Yak-18 and An-2 instruments and engine management i can write a small section about that

Sorry it's been so long, I had some school and medical issues that I had to deal with, but almost everything is in order now, so I'm going to explain the performance data information that I posted HERE.  To get the charts and information, you need to download the "Perf. Data file" in the post by clicking it and choosing "save as" or "save to disk", then you can open the files with Adobe Reader.  If you don't have Adobe Reader, you can download the free version HERE.

An important thing to remember about all these charts are that they are only estimates, they are not the exact performance you will get.  That is why we will be using the most conservative estimates with each calculation and why there are minimum fuel requirements for VFR and IFR flight.  Also, all altitudes are indicated altitudes MSL not AGL unless it says they are.

Alright, on to the good stuff...

----------------------------------------------------

Climb Performance Chart

This chart will give you the time to climb from one altitude to another, the fuel used during this climb, and the distance traveled along the ground during the climb in nautical miles.  Above the chart are some important things to note before using the chart.  This chart assumes that the climb is made with no flaps deployed and with full throttle, in a standard atmosphere (density altitude = pressure altitude).  Also, it's important to note that for fuel consumption calculations, you must add 1.1 gallons of fuel for engine start, taxi, and take-off.  The chart also assumes that above an altitude of 3000 ft, the engine is leaned for maximum performance (however, I've been taught to make all climbs with the mixture fully rich, at the altitudes that the 172 normally flies, the density will usually be within 80% of sea level density).  Also, the values of the chart can be adjusted by 10% for every 10°C above standard temperature and the values of distance during the climb assume that there is no wind, but these can be adjusted if you know the wind.  Also, the chart assumes an aircraft weight of 2300 lb (maximum take-off weight), which is a good assumption because it will always give you a conservative estimate for the values in the chart.

Now, to read the chart, you find your altitude and the altitude you plan to climb to, then read the values of the temperature, climb speed, and rate of climb for each altitude.  I usually average these values to get an estimate of what my airspeed will be, the average temperature, and my average climb rate.  These values aren't terribly important, as the rest of the chart will tell you the performance data you'll most likely need.  For the three columns on the right side of the table, you subtract the values for the altitude you plan to climb to from the values for the altitude you are at to get your time for the climb, fuel used during the climb, and the distance you travel during the climb.

So, as an example, say I'm flying at 3000 ft, and want to climb to 6000 ft.  Using the first three columns, I can find my average OAT (outside air temperature) will be approximately 6°C, I'll want to climb at approximately 71 kts, and my climb rate will be around 550 fpm.  Then, using the three columns on the right, my time to climb will be 10 min - 4 min = 6 minutes, the fuel used during the climb will be 1.9 gal - 0.9 gal = 1 gallon of fuel, and I will travel 12 nm - 5 nm = 7 nm.

Now, if the actual temperature were 12°C instead of the 6°C I found with the chart I could use the rule in the notes section of the chart.  Since 12°C is 6°C above standard temperature, we know there must be some correction, so as a conservative estimate we will just assume 10% above the values in the chart.  So, from before, our time was 6 min, so we will add 0.6 min, which will give approximately 6.6 min for the climb, and our fuel was 1 gallons, so we will add 0.1 gallon for 1.1 gallons used, and our distance was 7 nm, so we will add 0.7 nm for 7.7 nm traveled during the climb. 

So, if we had taken off at 3000 ft and climbed to 6000 ft, our values would all be the same, but we would add 1.1 gallons of fuel for start-up, taxi, and take-off, for a total of 2.2 gallons of fuel used in the whole first portion of the flight.

----------------------------------------------------

Rate of Climb Table

This table is similar to the climb performance table.  Again, it is assumed you use full throttle and no flaps in the climb, and the mixture is leaned above 3000 feet.

To read this table, all you do is find the altitude that you are at (or close to, or if you are between altitudes, you might want to average the nearest values, but this isn't really necessary), then just read over to find your climb speed, and your rate of climb according to the nearest value for the OAT.

----------------------------------------------------

Cruise Performance

This table looks a little complicated, but it is very similar to the rate of climb table from before.

To read this table all you do is find your altitude (or if you are between altitudes, you can round up for a conservative estimate), then find your engine RPM using the tachometer, and read over to find your engine power setting in % brake horsepower (BHP), or percentage of the maximum engine output, the airspeed this setting will give you in knots true airspeed, and your fuel burn rate in gallons per hour at these settings.

For example, you are flying at 4000 feet, with the engine at 2400 RPM in a standard atmosphere.  This will give you 64% of the engine power output, and a cruise speed of 110 ktas, and a fuel burn of 7.1 gallons per hour.

Again, if your altitude or temperature falls between the values given in the table, you can either interpolate to find something in between, or you can round up for a conservative estimate (usually the safer method).

----------------------------------------------------

Take-off Distance

A little out of order, but it will work.

The take-off and landing distance tables that are given in the information manual are for short-field operations, so they can be used to find the minimum distances required for landing and take-off.  If you aren't sure you can land your aircraft in a regular configuration, you can use the short-field data and procedures for landing so you can be sure.

For this table, it's very important to take note of the conditions and notes at the top of the chart.  For the short-field take-off, the chart assumes you are using no flaps, however, as I was taught, and as Brett outlines HERE, 10° of flaps are usually used on short- and soft-field take-offs.  Also, the chart assumes you taxi to the runway and apply the brakes before applying full power so you don't have to wait for the engine to reach full power output after applying full throttle.  For the values in the chart, the table assumes a flat, dry, paved runway, and no wind, which might not always be the case, however, there are some corrections that can be made if this isn't the case.

Next, the notes sections details the corrections that can be made to the values in the chart if the conditions aren't the same as the chart assumes.  The chart assumes a short-field take-off technique is used, as Brett explained HERE, and that the mixture is leaned above 3000 ft for maximum RPM.  The next two corrections are very important.  Since it is a very rare day when there is no wind, the wind correction is extremely important.  First, you must use a crosswind component calculator, like THIS ONE, to determine your headwind component on take-off, then use the correction in note #3 to adjust the value you find in the table.  Also, if you are flying from a grass runway, you must increase the ground roll by 15% because of the increased friction.

To find your take-off roll, you find your pressure altitude in the third column, then read over to the temperature that is the next highest above the actual temperature (if it's 8°C, use the 10°C column, or if it's 14°C, use the 20°C column for conservative estimates), and find your ground roll, and the distance required to clear a 50 ft obstacle that is in your flight path (trees, buildings, power lines, etc...).  Also, it's important to note that the chart assumes a 2300 lb total weight, and that you lift-off at 50 KIAS, and climb at Vx (59 KIAS in the 172).

Next, make any corrections for wind speed or runway conditions that are necessary.

----------------------------------------------------

Landing Distance

The landing distance table is almost exactly the same as the take-off distance table, except it assumes you are landing with full (40°) flaps, no power, and that you use maximum braking on landing.  Now, this is somewhat off, because to get these values, test pilots land in as short a distance as possible.  This means they slam the airplane down and jump on the brakes to come to a screeching halt (or something like it).  This is something you won't want to be doing on a regular basis, and since you will need a little extra distance for landing, you'll probably want to add a bit on to the value you read in the table. 

----------------------------------------------------


Next post will discuss the weight and balance charts...

In this post we'll discuss the weight and balance calculations to determine whether it is safe to fly the aircraft.

It's extremely important in flying to determine the how heavy the aircraft will be when you're fully loaded and the location of the center of gravity (CG).  An aircraft in-flight is a lot like a teeter-totter, with the center of pressure (where the lift force is applied) as the center of the teeter-totter, the CG is on one end of the teeter-totter, and the lift force from the tail is on the other end of the teeter-totter, as shown in the picture below.  In the picture, the blue arrow is the lift force generated by the wings, acting at the center of pressure, and the front red arrow is the weight of the aircraft and passengers, acting at the center of gravity, and the back red arrow is the lift being generated by the tail.  Notice that when the center of gravity is in front of the center of pressure, the tail actually produces a lift force downwards, opposite the lift generated by the wings.  This is a desirable situation because if, for some reason, the tail wasn't producing any lift and the center of gravity was behind the center of pressure (opposite the picture), the aircraft would want to pitch up on it's own, and would eventually stall and be uncontrollable.  If the CG is in front of the center of pressure, the aircraft will want to pitch down, and the airflow over the control surfaces allow some degree of controllability.



Now, if the center of gravity is too far forward or too far backward, the lift forces generated by the horizontal stabilizer will not be enough to allow the pilot to keep the aircraft level, and the aircraft will either never get off the ground (too far forward), or the aircraft will pitch up too soon (too far backward), and stall on take-off and fall back to the runway.  Because of this, it is extremely important to calculate where the CG will be, and whether or not it is within the limits for your aircraft.

One important concept to understand is that of a torque, or a moment.  Using the teeter-totter again, imagine that you have a very fat man, sitting very close to the center of the teeter-totter.  You could balance him out by having another very fat man sit very close to the teeter-totter, or you could have a skinny man sit very far from the center of the teeter-totter.  The torque results when you have the force from the weight of the man acting at a distance from the center of the teeter-totter.  So increasing the force applied increases the torque and increasing the distance from the center increases the torque.  THIS might be a better explanation of torques and moments.

The following charts will allow you to easily calculate the important values for only the 1979 Cessna 172N we're talking about.

---------------------------------------------

Weight and Balance Sample and Loading Graph

This table is a handy way to calculate how everything will affect the weight and balance of the aircraft.  We'll use the values that are used in the sample problem in the left columns.  The "weight" column is the column where the weights of the aircraft, fuel, passengers, and luggage are input, and the "moment" column are where the torques, or moments are calculated.

The very first thing that must be done is to calculate the weight of everything going into the aircraft except for the fuel.  This includes the pilot, passengers, and luggage.  This value is added to the weight of the aircraft to determine how much fuel can be carried.  In the sample problem everything (minus the fuel) weighs 2060 lb.  Since the maximum take-off weight is 2300 lb, that means that 240 lb of fuel can be added without going over the maximum weight.  At 6 lb of fuel per gallon, this is 40 gallons of fuel, and at approximately 8 gallons per hour in flight, this is about 4.5 hours of flight time with VFR reserves.

Now, starting with the first row, the weight of the aircraft with no fuel and full oil is 1454 lb.  The moment arm for the weight is already calculated, and fixed for this aircraft, so the moment that results is 57,600 lb-in (note that the values in the second 'moment' column are divided by 1000).

Next, the fuel required was calculated before, and is 240 lb.  The moment arm for the fuel is calculated using the "Loading Graph".  To use the loading graph, read up the left side to the weight you need, then go across the graph to the line for whatever you are looking for (in this case, the "Fuel" line), and read down to the bottom of the graph to find the moment that results.  In this case the resulting moment is 11.5 in-lb (x1000).  Input that in to the table. 

Next, using the weight of the front seat pilot and passenger, the rear passengers, and the baggage, us the loading graph to find the moment for each.

Then, the total weight and moments can be added together to find the total ramp weight and moment.  In the sample, they assume that 7 lb of fuel are used for startup and taxi so the total take-off weight and moment are 2300 lb and 103.6 in-lb.

Next, use the remaining two charts to determine if these values are within the limits specified.

---------------------------------------------

COG Moment Envelope/COG Limits

These charts will both tell you whether or not you are within the limits for your aircraft.

To read the COG Moment Envelope chart, you find the weight of the aircraft on the left side of the chart, and the moment you calculated on the bottom of the chart, and see if the point where these two intersect are within the outlined area.  If they are, you are safe to fly.  If they aren't, you'll have to adjust the loading of the aircraft until they lie within the limits.

To read the COG Limits chart, you use the same method as the COG Moment Envelope chart, except you have to divide the moment you found by the weight to get the moment arm.  You then find this value on the bottom of the chart and read up to the weight of the aircraft to see if you are within the outlined envelope.

---------------------------------------------


Now, most of this is different from the data Brett used earlier for the demo flight, but it should give you an idea of what must be done for a flight to be safely conducted.  But, I don't know of any pilot who does all this work on each an every flight they go on.  If you fly by yourself, or with one or two other passengers who you know won't put you over the maximum weight, and you don't fly on quarter full tanks to an airport 100 miles away, you will most likely be quite safe in doing so.  However, it's important to know this data, and be quire familiar with it in case something happens (you get stuck above the clouds, passengers freak out, etc...), you don't want to be up there trying to remember all this data while you're flying.  So, if you're ever (ever, ever, ever) in doubt, just do the calculations quick.  It shouldn't take more than five or ten minutes if you're familiar with them.

You got it !  (I'm not checking your math, but I'm sure it's correct) 

Now.. couple that endurance (1.8 hours) to your ground speed (adjusting for winds aloft), and you've got your maximum range..

Point of wording and accuracy:

You said: Quote:



TAS (true airpseed) is not the same as ground speed. I know, you know this.. but I'm compelled to point it out for others who might stumble in.

For the record:  True airspeed is indicated airspeed adjusted for density altitude. (there's another step in there called calibrated airspeed, but the difference is insignificant in planes traveling at these speeds and at these altitudes)... Ground speed is true airspeed adjusted for the winds aloft.

One thing to remember is your VFR reserve fuel - the fuel required to get to your destination plus 30 minutes extra (usually 4 gallons assuming an average of 8 gallons per hour).  Also, if your using the data I posted, the fuel tanks hold 54 gallons total, with 4 gallons unusable, giving you 50 usable gallons, or 46 usable gallons with a VFR reserve and full tanks.

I'll jump in  

Mobius summed up the Indicated/Calibrated/True airspeed stuff nicely. All I'll add, is that with airplanes flying at the speeds and altitudes that 172s fly; calibrated and indicated airspeeds are pretty interchangeable... And you can get a good guess at true airspeed (in-flight only.. NOT for planning purposes) with the calculator built into the airspeed indicator. I'm pretty sure it works in the MSFS C172. It's the little slide ring around the gauge itself.

There are two inputs. Outside air temperature / pressure altitude. Obviously, you get the temperature from the OAT gauge, and pressure altitude can found by temporarily setting your altimeter to 29.92.



Slide the ring until the pressure altitude is lined up with the outside air temperature.. and then you can read the true airspeed.

In that photo, the indicated airspeed is ~92knots.  If the slide ring were set accurately (for example  OAT is ~5  and  pressure altitude is ~5,000), the true airpeed shows ~95knots.

A neat thing to note here, is how much temperature can effect atmospheric density (density altitude). Looking at that ring you can see that if it were a standard day pressure-wise (29.92), and the OAT was ~95... then indicated airspeed would show the same difference from true airpeed at sea-level, as it would at 5000 feet on a day when the OAT was ~5.  

Pitot heat for a C172 brings on interesting debate. The only hard-n-fast rules I live by, are to never turn it on until you're airborne (because you can burn the element out sitting on the ground), and to always turn it on for instrument flying. 47F seems like a good benchmark for using it, otherwise..  but the thing is.. if you have a chance of picking up pitot ice; you have a chance of picking up airframe ice, too. So you shouldn't even BE flying.

We have several C172s in our club. The C172P's are 180HP and have the 26.5 gallon tanks.. the C172N's are 160HP and have 20 gallon tanks.

The MSFS is 180HP, and obviously has the 26.5 gallon tanks.

I asked a veteran instructor.. he said the 26.5 gallon tanks end up with about 1.5 gallons unusable (total of 3)..  the 20 gallon tanks about 1.25 gallons unusable (total of 2.5).

Ice... a chilling topic... 

EG7's deduction is sound, but let's not forget our "friend", carb ice (although it's not a worry in the default FS Skyhawk).
I've managed to avoid airframe ice in RL so far (which is pretty easy when you're not instrument-rated), but I did experience carb ice once... and there was only a high broken cloud deck, but visibilty was good, which often suggests low moisture content near the surface.

   I don't recall the dewpoint spread that day (although it was darn cold), but I do remember that it must have been on the dry side- I sure wasn't expecting the carb of my rented 172 to ice up while I was cruising flat-out at about 2000 MSL!   

  The carb heat got rid of it quickly while I used airspeed to gain a little altitude (over the Palisades just north of the G. Washington Bridge, which is not a fun place to lose engine power), but it was a sobering lesson: when it comes to carb ice, visible  moisture does not apply when the ambient temperature is low. Air always has a little water in it, and in the low-pressure environment of a Venturi inlet, not much is needed sometimes to create condensation and then ice.
In warmer weather, even hot weather, carb ice can still form, but conditions have to be quite humid, as far as I know.

I did hear all about that in ground school, of course, but nothing drives that stuff home better than watching the tach drop, then drop even more as you apply carb heat, while you're hoping it won't get worse before you reach your destination!   

Hello, Brett. I just wanted to thank you for taking the time to write out these fantastic articles. They are pretty much exactly what I've been looking for. "Real" training for MSFS. I haven't read any of it to any extreme depth, only a skim so far, but they look great and I fully intend to follow them all the way through to number seven. I also read several mentions of you doing some more advanced stuff like instrument approaches, advanced navigation, etc. I would like to put in my vote for a PLEASE DO! I would love to learn this stuff.

I only fly FS2004, so I wouldn't be able to take the "checkrides" unfortunately, but I assume that everything else would still apply.

By the way, one neat little trick I picked up from my random skims of your articles... The trick of pinpointing your location by dialing in two VOR radials and seeing where they intersect. That is awesome!

Thanks!

Good question  

Deviations from standard temp ( 15C at sea level.. and it changes with with changes in altitude.. so it's not a good constant))..  would require extra math. No big deal if you get used to it. And for all I know, there are airspeed indicators out there, set up that way.

Just think about the temperature range.  

-30 to +30  Celsius  =  -22 to +88  Fahrenheit..

If it were -30 to +30 Fahrenheit (not that you thought it might be); it wouldn't allow for a temperature above freezing (32F).

It's horribly innacurate anyway. By the time you'd be genuinely concerned with the difference between indicated airspeed and true airspeed in flight (in slow, low-altitude airplanes)... you'll be good at estimating it. Altitude is the biggest factor.

I've got a quick question about wind direction.  If wind is given as 260* @15kts, is the wind blowing towards 260* or from 260*? It is so simple, but I'm just not sure which is correct. And, it will make a big difference in a flight plan.

I've been lurking around these lessons for a while now and really have learned something from them.  I have also taken the time to do a lot of the lessons in fsx. I am getting the hang of VOR flight, and am able to control my aircraft much more precisely.

I used to be one of the "instant airline" pilots out there, but now I get more enjoyment in a C172 or Maule Orion then I get from the 737 or the like.

I would like to come up with a flight plan here when I get the time, but I'm not sure when it will happen. Soon hopefully.

markag

Ask away indeed.    Much more is learned by all, when questions are discussed.