Sim Flight Training: PPL: Part 1 of 7

[Mobius]

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.

[Mobius]

Ahh, could be an error on my part.  Standard Cessna fuel tanks hold 21 gallons each, so 42 gallons total.  I'm not sure if that's with or without the unusable amount.  My data is for the 172 equipped with long range tanks (the 54 gallon tanks), and I'm not sure which one FS models.  It sounds like FS only has the standard tanks?

Also, with the airspeed, an important thing to consider is the different types of airspeed:

Indicated Airspeed - this is the airspeed that is read directly off the airspeed indicator from the pitot-static system.

Calibrated Airspeed -  this is indicated airspeed corrected for position, instrument, and installation errors.  There is a table of calibrated airspeeds for different indicated airspeeds in the 172 POH.  I didn't include this in the performance data file, but I can scan it and add it this weekend.  It usually doesn't vary by much more than a couple knots.

True Airspeed - this is calibrated airspeed corrected for non-standard temperature and altitude.  This usually takes a little math to figure out, but it can usually be estimated relatively accurately with a TAS calculator, like this one:  http://www.paragonair.com/public/aircraft/calc_TAS.html

So, when you say you are supposed to be flying at 126 kias, but you can only go 108 kias, you're reading your indicated airspeed off the AI, but your true airspeed is somewhere around 125 kts (using the handy calculator, 6000 ft altitude, 28.95 altimeter setting, and 80

[Brett_Henderson]

I'll jump in

[Brett_Henderson]

And for the fuel in the MSFS C172...

[Brett_Henderson]

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..

[Brett_Henderson]

This is great discussion...

As far as icing and a C172 goes (especially in a Gulf climate). It's not really a concern. Before anyone jumps on me, let me elaborate. Pitot ice, and airframe ice don't form under the same conditions as carb ice.

Your concern about realtive humidity and cooler temperatures (even well above freezing), show that you're DEFINATELY getting the pilot's frame of mind working (the whole reason I started these threads)


Carb ice is a product of the super-cooling that happens when you compress and then decompress a gas (even plain old air). It's the same theory behind air-conditioning and refrigeration (except the gas lends itself better to the effect). When air enters a carb venturi, it gets accelerated and hence compressed, because the same volume of air is forced through the carb and then it gets decompressed as it enters the realtive lower pressure of the intake manifold. Remember the last time you blew dust out of your computer with a can of compressed air ? As you DEcompressed the air, the can got very cold, very fast. That's the same phenomenon that causes carb ice.. and why carb heat is needed ESPECIALLY when you reduce power... because you're increasing the compress/decompress ratio as the carb's throat gets restricted by the throttle "butterfly".

In order for airframe ice to occur, the actual outside air temperature has to be below freezing.. AND the realtive humidity must be high enough that water vapor is visible. You won't pick up airframe ice flying in clear, mist/cloud-free air.. no matter how cold it is.

Pitot ice is a little different.. Kind of in between, because there can be a venturi effect .. but it's almost insignificant. Heck, if you wanna split physics hairs, there's a compress/decompress effect created by an airfoil, as it moves through the air. Again though... far from a concern for C172 pilots.

The main use for pitot heat in small, GA planes is to avoid that surprise pitot/static failure. And why it's always used when flying by instrument. Scary, creepy things can happen when pitot tubes and static ports ice over. And they'll likely ice over before you can get a sense of any airframe ice forming.

Consider this:

[beaky]

Ice... a chilling topic...  ;D

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!  

[Brett_Henderson]

I've never experienced carb ice. There was one time however, when I went to add a little power on final, and the engine wasn't as responsive as I expected. I haven't landed a carb-equipped airplane since, without carb-heat applied, no matter what the temperature/humidity.

[BTilson]

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!

[Brett_Henderson]

I'm glad you're enjoying them  :)

VOR navigation is fun stuff.. and represented very well in MSFS.

I'm gearing up for Sim Instrument Ground School... I just want to take the time to do it properly...

[Brett_Henderson]

Good question

[Slotback]

And just for good measure:

Celcius to Fahrenheit     = 1.8 x Celcius + 32.
Fahrenheit to Celcius     = Fahrenheit -32 / 1.8

[markag]

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

[Mobius]

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.

That means the wind is blowing from 260

[Brett_Henderson]

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