Ground School

Friday, June 13, 2008 - 15:50:09 ET

Calculating Legal Night

One thing you need to do that wasn't really taught (to me) was how to calculate when you're flying at night (or Legal Night as us pilots like to call it).

This is important for a few reasons:

- If you don't have a night rating, you need to know when you need to be wheels down and engine off.
- If you do have a night rating, then you need to know when you can log your hours as night.
- I'm sure airport operators needs this information for when to turn various lighting systems on or off.

First, lets define when nighttime for the purposes of aviation and your log book starts and ends.

GEN 1.6.2 Says:

In the morning, Twilight begins when the sun is 6° below the horizon ascending, and ends at sunrise, approximately 25 minutes later. In the evening, Twilight begins at sunset, and ends when the sun is 6° below the horizon descending, approximately 25 minutes later.

Who did what in the where now?!? In other words...

Dawn is 25 minutes before sunrise, Dusk ends 25 minutes after sunset.

So we know when Twilight starts and ends for both the morning and evening. How does that apply to finding out when it's nighttime? We need to turn to CAR 101.01 for that:

"night" - means the time between the end of evening civil twilight and the beginning of morning civil twilight; (nuit)

So in other words, "night" for the purposes of aviation starts 25 minutes after sunset and 25 minutes before sunrise.

Great! So uhmm.. how do I find out when sunrise and sunset are? Here are a few ideas:

- Hand held (and probably aviation) GPS units have that information in a menu someplace.
- You can ask ATC (especially if its an FSS you're talking to)
- You can use the graph found in the AIM.
- You can use the internet, specifically the NRC website.

No matter what way you use to get the information be sure you do the following:

- If you are given values for sunset and sunrise, add 25 minutes to the sunset time, and subtract 25 minutes from the sunrise time to give you legal night.
- If you are given values for civil twilight start and civil twilight end, then do not apply any correction to the time.

This is another reason to keep track of your start-up and shut-down times. As this can occur on a day/night boundary. Ie, you need to log your 2 hour flight as 1.1 in day and 0.9 in night.

Comments (4) | Permalink | Category: Air Law

Friday, April 4, 2008 - 13:26:25 ET

Airports, Aerodromes, and Grass Strips

A friend of mine mentioned that it would be cool to have "a million dollars" to have his own airport. I told him that all you need is space to land an airplane and you can do just that, legally.

Without referencing anything, I told him that you are allowed to land on private property as long as you have permission. If you own the land, then there should be no question as to the legal ramifications of landing an airplane on your parcel of land.

The conversation ended there but I decided to look further into things like getting your "airport" listed in the CFS.

Let's start with the most basic of aerodromes. A grass strip on your farmland. It's literally just a 3000 foot by 50 foot strip of mowed grass. Just enough to get your 172 airborne and land safely.

Since the winds in Canada are primarily from the west, your strip is orientated in an east/west direction. Runway 27/09.

You own the land. Therefore you have the right to land and take off your aircraft from that grass strip. Your friend asks you if he can use it to, you say "yes". He is now legally allowed to land on your grass strip.

After a summer of take-offs and landings at your grass strip, your neighbour starts complaining that what you're doing is illegal.

CAR 602.14(2) states that you are allowed to fly "low" and close to people or property as long as you are conducting a take-off or landing. As long as you're not buzzing your neighbours house, what you are doing is totally legal.

Yes, your grass strip is technically an "Aerodrome".

The following year you've added a windsock so that you can tell which direction the wind is coming from. You also would like to add your aerodrome to the CFS so that fellow pilots can find information about your grass strip.

Since there is a windsock now, the minimum requirement for registering an aerodrome, you put your request in to the Minister to add your aerodrome to the CFS. CAR 301.03 outlines what minimum requirements are needed before you can register your aerodrome.

Technically, you don't even need a windsock if you are able to determine the wind direction by means of smoke, or ripples in water.

Your little grass strip is now a registered aerodrome. It will appear in the CFS and on aeronautical charts.

I have noticed a few such aerodromes in the CFS. Particularly New Liskeard (CPX3) aerodrome. This aerodrome interests me because it is close to Cobalt, Ontario. The town my girlfriend grew up. I think it would be cool to visit her family one day by plane.

Anyways. Pretty much anyone can have a registered aerodrome in Canada. If you'd like to run an airport, well thats a different cup of tea.

Registration means it appears in the CFS and is registered with the Government as an aerodrome. The registration of an aerodrome with Transport Canada is handeled by each regional office of TC. The registration form for an aerodrome in Ontario can be found here.

Certification means that it is an airport and compiles with CAR 302. this includes things like having an Airport Operations Manual, application for a certificate, and minimum obligations of the airport operator.

Comments are welcome.

Comments (3) | Permalink | Category: Air Law

Thursday, March 13, 2008 - 21:42:55 ET

Calculating G-Forces in a Turn

A while back I posed the question "Does an airplane in 45° bank experience more G forces than a slower one?"

The quick answer: No. The G forces (or load factor) on the aircraft does not change based on the speed you are flying.

The equation to calculate load factor (n) is as follows:

Where Theta is the angle of bank.

Since the angle of bank determines the load factor and not speed, a faster aircraft at 45° will experience the same load factor of a slower aircraft at the same angle of bank.

The only thing that is different is the radius of the turn. A faster moving aircraft will have a larger turn radius at the same angle of bank than a slower aircraft.

In all instances we're talking about true air speed (TAS).

So lets use two aircraft. A Cessna 172, and a Piper Seminole. Both are excecuting a 45° bank turn. The 172 at 90KTAS and the Seminole at 130KTAS:

Cessna:

Seminole:

This is important information to know, especially if you are flying in canyons or other places with limited area to maneuver. If you need to turn 180° in the smallest amount of distance, its best to slow down before executing the turn (see comments).

Don't forget! Your stall speed increases as the angle of bank increases.

I was never good at math, so please correct me if iIm wrong. The formula states "velocity" and not speed. So I'm unsure if I can use KTAS or if I need to convert that into feet per second.

Oh and where did I get 11.29? See the bottom of this page.

Comments (6) | Permalink | Category: Aerodynamics

Sunday, April 22, 2007 - 21:19:21 ET

Landing at an Uncontrolled Airport

There are two "types" of uncontrolled airports, both of which have different rules and procedures.

An uncontrolled aerodrome is one where a control tower does not exist or is not in operation. For example, Buttonville is an uncontrolled aerodrome while the tower is closed (between 2300-0700 local time).

Because the traffic is not controlled, it is important that users of the aerodrome follow the procedures exactly. This ensures that your actions are predictable to other traffic that may be coming and going.

Mandatory Frequency
Aeordromes with a MF specified in the CFS must use this frequency when communicating your intentions to other pilots in the area. This can be a UNICOM or a RCO or a FSS.

In most cases you will be directing your calls to "radio". For example, if you're landing at Muskoka, you'd be broadcasting your radio calls to "Timmins Radio". In this example I usually make the call as "Timmins Radio at Muskoka".

There is a set of calls that must be made in an MF control zone:

(CARS 602.101)
- 5 Minutes before entering the zone. Give your position, altitude, and intentions on how you plan on entering the circuit.
- When joining the circuit
- When on the downwind leg (if applicable)
- When on final approach
- When clear of the active runway

This ensures that everyone else in the area knows where you are and what you're going to do.

When it comes to joining the circuit, there are only two ways:

- Mid-Downwind Leg
- Straight in Downwind Leg

However, if there is traffic advisory available, you may enter the circuit by using the method outlined in the ATF section below.

Aerodrome Traffic Frequency
Aeordromes with an ATF specified in the CFS must use this frequency when communicating your intentions to facility responsible for the airport. In most cases this is an UNICOM.

In most cases you will be directing your calls to "traffic". For example, if you're landing at Peterborough, you'd be broadcasting your radio calls to "Peterborough Traffic"

The same set of calls that you must make at a MF aerodrome are needed at an ATF aerodrome.

When it comes to entering the circuit, your options are as follows:

- Straight-In Downwind Leg
- 45° to the Downwind Leg
- Straight-In Base Leg
- Straight-In Final Leg

(Similar to your options at a controlled airport).

Things To Consider
- If no ATF or MF are published, use 123.2 Mhz
- Some pilots operating under VFR at many sites prefer to give commercial IFR and larger type of aircraft priority. This practice, however, is a personal airmanship courtesy, and it should be noted that these aircraft do not establish any priority over other aircraft operating VFR at that aerodrome.
- IFR Approaches may be made at an uncontrolled airport. If you are a VFR pilot, try to get familiar with what is involved with a "circling approach" so you will understand what an IFR aircraft will do when trying to land at this airport.

Comments (7) | Permalink | Category: Air Law

Saturday, December 23, 2006 - 13:29:18 ET

Ground Briefing Study Lesson #1

Documents and Airworthiness
Q: With respect the Air Regulations, what documents are required to be on board for every flight.
A: Certificate of Registration, Certificate of Airworthiness, Weight and Balance Report, Journey Logbook, POH, Licences (radiotelephone medical, and pilots licence), Interception Orders, proof of insurance.

Certificate of Registration
Q: What does the Certificate of Registration tell you?
A: Gives the nationality and registration mark, aircraft manufacturer, model and serial number, the purpose, name and address of the owner, owner registration date, certificate issue date, and signature for the Minister of Transport.

Q: How long is the Certificate of Registration valid? What invalidates it?
A: Remains valid as long as the ownership does not change, or the owner's address does not change. It becomes invalid when the aircraft is destroyed or taken out of service permanently.

Q: How long does the owner of an aircraft have to notify the Minister of Transport for a change of address?
A: 7 Days

Q: What is the procedure with respect to the Certificate of Registration when the aircraft is sold?
A: To effect a change of ownership, the reverse side of the Certificate of Registration must be filled out and mailed to the Minister of Transport within 7 days.

Certificate of Airworthiness
Q: For how long is the original Certificate of Airworthiness valid?
A: Indefinitely, if the aircraft continues to meet the conditions under which it was issued, that is, as long as the aircraft is maintained in accordance with the requirements of the controlling agency.

Q: What temporarily invalidates the Certificate of Airworthiness?
A: Failure to comply with Airworthiness Directives, failure to do required maintenance, an action that contradicts the POH, minor or major accident, snag written in the journey logbook.

Q: How often must the Certificate of Airworthiness be re-validated?
A: Once a year of every 100 hours, whichever comes first.

Q: How is it revalidated?
A: By submitting an Annual Airworthiness Information Report

Q: Is a Certificate of Airworthiness issued for amateur-built aircraft?
A: No, Amateur-built aircraft are issued a Flight Permit

Weight and Balance Report
Q: Define Basic Empty Weight (BEW)
A: BEW includes: Weight of the standard airplane, all optional equipment, full oil.

Q: Define maximum takeoff weight
A: Maximum takeoff weight is the maximum weight approved for the start of the takeoff run.

Q: How does the maximum take off weight differ from the maximum ramp weight?
A: Maximum ramp weight includes the fuel that will be used for start, taxi, and run-up. Therefore, as a result of the fuel already burned, maximum takeoff weight will be less than maximum ramp weight.

Q: Who prepares the Weight and Balance document that must be carried on board?
A: The weight and balance document is prepared by the manufacturer of the aircraft.

Q: Show the actual Basic Empty Weight and Gross Weight for the test aircraft.
A: Produce, for inspection, the weight and balance report for the aircraft actually used for the flight test test.

Q: What is the difference between normal and utility categories?
A: The utility category is solely for the purpose of training pilots in certain flight manoeuvres and, therefore, is usually subject to some restrictions. The normal category, maximum gross weight operations are permitted, but certain manoeuvres, such as spins and steep turns, are prohibited.

Q: What can the pilot learn of the categories for which the aircraft is approved as well as any related limitations?
A: Take a look inside the POH

Q: Is an aircraft considered airworthy if overloaded? Why?
A: No. Compliance with weight limitations is part of the airworthiness validity.

Q:How often does an aircraft have to be re-weighed?
A: If a change in weight of more than 2% of the empty weight has occurred.

Q: What important information is found on the original Weight and Balance Report that will not be found elsewhere?
A: Date of manufacture of the aircraft, the actual unusable fuel, the amount of full oil.

Comments (3) | Permalink | Category: Air Law

Wednesday, September 27, 2006 - 21:29:14 ET

How to intercept a NDB track

I am going to illustrate how to intercept a NDB track using MS Flight Simulator 2004 in a perfect world (no wind to worry about).

There are certain times that you will need to track to a NDB at a particular heading. This is mainly used in two situations:

1. You are using NDB (LF/MF) airways.
2. You are using a NDB approach into an airport.

In this example we want to intercept the Buttonville (KZ) NDB at 150°.

Step One - Tune and Identify
The first step involves tuning your nav radio to the Buttonville NDB frequency. You can find this frequency on any chart (VTA, VNC or an IFR LO chart). It is also located in the CFS. Tune your radio to 248kHz (1) and pull the volume knob to listen to the Morse code (2).

If you don't hear any Morse code, then the station is un-serviceable and cannot be used for navigation. If you hear Morse code and it is not what is to be expected, double check your frequency.

Step Two - Parallel Your Track
Once you have the NDB station tuned. You need to find out at what heading you need to fly in order to intercept this track.

Turn your airplane to a heading of 150° (3) and note that the bearing to the NDB station is 50°^[1] to the right (4).

The rule of thumb to use is to add 30° to your bearing to station and turn that many degrees towards the ADF needle. There is one exception though. You never want to turn more than 90° so you add 30° to whatever your ADF needle shows to a maximum of 90°.

In this case 30°+ 50° = 80°

Step Three - Intercepting The Track
Turn 80° to the right. 80° + 150° = 230° (5) You will notice that the ADF needle has moved(6). You want to keep flying this track until the needle has moved 80° to the left (when it reaches 280°)

Step Four - Flying To The NDB
When the ADF needle gets 80° to the left (when it shows 280°) it is time to turn!(7) Turn to the heading that you want to intercept the NDB at, which is 150°(8)

Just keep on this heading and you will cross over the NDB. You will notice that the bearing to the station is 0° (because the needle is pointing to north)(9)

How do you know when you've crossed over the NDB? When the needle swings 180° and points behind you.(10)

^[1] Note: When I originally performed this exercise I noted the bearing to station in step two as being 050° instead of 055° This is why the ADF needle in figure 9 is pointing to 005° instead of 000° This error is also noted on my ground track as I don't fly directly over the station.

Comments (0) | Permalink | Category: Instruments

Saturday, April 8, 2006 - 23:47:54 ET

Hazardous Attitudes

There are five types of attitudes that can be considered "hazardous". It is these attitudes that make us do things that have consequences that outweigh the reward.

Anti-Authority
Someone who "breaks the rules". The thinking of "I know better than the boss" falls under this category.
Example: Not following SOP or the CAR.

Impulsivity
Reacting before spending some time to think about your actions.
Example: Skipping items in a checklist because you're in a rush. Not doing a HASEL check because you're pressed for time.

Invulnerability
"Oh, nothing's going to happen to me" or "Bad things always happen to other people". Not thinking your actions will effect you at all.
Example: Someone who thinks they can do anything because they've been flying for many years.

Macho
Doing things you wouldn't normally do to fit in. Showing off to earn respect or impress someone.
Example: Trying to impress your captain by attempting a landing you're not comfortable with. Impressing friends by doing acrobatics when you're not trained/certified.

Resignation
Giving up when you know you're right. This usually happens when you're challenging someone of authority or above you.
Example: After telling the captain a couple of times that something doesn't look right, and he dismissing you each time, you give up.

At least one of these attitudes can be found in each aviation accident.

Comments (3) | Permalink | Category: Human Factors

Saturday, March 11, 2006 - 16:56:08 ET

The Three Altitudes

A plane needs air to be able to fly. Thanks to the laws of physics, the same parcel of air can have different characteristics based on temperature and altitude. Because of this, there are a few things we have to be careful of while trying to keep that hunk of metal afloat.

Let's take a look at some fundamental "laws" of air (and all gases for that matter), as they apply to flying:

- As altitude increases, air pressure decreases
- As air temperature increases, air pressure decreases (Gay-Lussac's law)
- As relative humidity increases, air pressure decreases

These three items are very important because aircraft performance is based on how much air it can move over its wings at any one time. The more air (dense) the aircraft can use for propulsion and lift, the better the aircraft will perform. For this reason, we calculate pressure altitude and density altitude.

Calculating these values are key especially during take off.

To calculate at what equivalent altitude you'd be taking off from, use this formula:

(ICAO Standard Pressure - Current Station Pressure) * 1000 + Station Altitude (in feet).

Lets take a look at calculating pressure altitude at an airport that is 650' above sea level (Buttonville) with a current station pressure of 30.23" Hg:

(29.92"Hg - 30.23"Hg)*1000+650' = 340'

So at 30.23"Hg station pressure, you'd be taking off from a pressure altitude of 340'. Lower altitude means denser air, which means better performance. In essence, every 0.1"Hg of pressure equates to 100'.

Now, the pressure altitude equation above assumes the stations air temperature is 15°C and dry. This is hardly the case (especially in Canada). This is why we figure out density altitude. Which is the true indication of your actual "altitude". Calculating the density altitude can get a little complex. This is why we have our E6B calculators!

I hope that this explains why flying in the summer in Toronto is such a pain in the ass. Really hot and humid weather is not ideal flying conditions. Let's assume its a really nice muggy day at Buttonville (650' above sea level). The temperature is 30° with a dew point of 28°C. Station pressure is 30.15"Hg. Using a calculator the density altitude is 2745'. This means that at Buttonville, you'd be trying to take off as if your plane was 2745' above sea level.

Comments (3) | Permalink | Category: Airmanship

Sunday, December 4, 2005 - 23:50:39 ET

Learning your A,B,C's

Take a look a the map that I photoshopped the other day as a reference. Today I'm going to talk about the different classes of airspace around Buttonville.

There are actually 5 classes of airspace around Buttonville, but you can only see four of them on my map.

Lets start off with what you can see and I've highlighted.

Class Charlie
Class "C" (or Charlie) airspace is the most common (I think) airspace in and around Toronto.

Rules:
- You must have a radio
- You must have a transponder
- You must have clearance before entering the airspace

Services offered:
- Conflict resolution upon request (help with not colliding with anyone)
- Air traffic information (who is where)

For VFR flight inside class charlie you must be 500' below any cloud and 1 mile horizontally away from cloud. 3 miles of visibility minimum.

Class Delta
Class "D" (or Delta) airspace is found around some of the more active smaller airports in the area.

Rules:
- You must have a radio
- Transponder only in designated areas
- You must establish radio contact before entering (you dont need to ask to enter, just let them ATC know where you are)

Services offered:
- Conflict resolution conditions permitting (if the controller has time to)
- Air traffic information

For VFR flight inside class delta you must be 500' below any cloud and 1 mile horizontally away from cloud. 3 miles of visibility minimum.

Class Echo
Class "E" (or Echo) airspace is found around only at the Downsview control zone. I have no idea why.

Rules:
- Transponder requred in designated areas
- Radio optional
- No clearance or radio contact is required before entering.

Services offered:
- Air traffic information conditions permitting

For VFR flight inside class echo you must be 500' below any cloud and 1 mile horizontally away from cloud. 3 miles of visibility minimum.

Now for the items you cant see on my map.

Class Foxtrox
Class "F" (or Foxtrox) airspace is also known as restricted airspace. There are specific rules governing the use of that airspace. The closest location of Class Foxtrot space is located north of the Oshawa aerodrome. It is reserved for flight training.

Class Golf
Class "G" (or Golf) is located "everywhere else" and is also known as unrestricted airspace. This is the area where no other classification is given below 18000'.

Rules:
- None

Services offered:
- Flight information and alerting (weather, flight planning, etc..)

For VFR flight inside class golf you must be clear of all cloud and 2 miles of visibility minimum below 1000' AGL. Above 1000' AGL you must be 500' below any cloud and 2000' horizontally away from cloud. 1 mile visibility minimum.

Phew! I'm sure I can remember all this.

Comments (3) | Permalink | Category: Air Law

Saturday, December 3, 2005 - 23:27:45 ET

Learning About Airspace

I spent some time today looking at the Toronto VTA and the CFS entries for Buttonville (YKZ), Downsview (YZD), Pearson (YYZ), and Toronto Island (YTZ) airports. My goal was to try and understand the airspace around my home airport (Buttonville).

I think I've figured it out. But first, some definitions:

Control Zone
Those are the highlighted areas around the aerodromes (blue for class "C" airspace, red for class "D" and green for class "E"). Their purpose is to offer better control between IFR and VFR traffic. They are only present around aerodromes with a tower (notice the lack of a CZ around the Makrham airstrip to the north east of buttonville).

Terminal Control Area
You can see this area on the map by the blue radiating lines around Pearson. It's purpose is to control IFR traffic to arriving and departing aircraft. The space between the floor of the TCA and ground level is uncontrolled. For example, at the 15NM marker, the TCA is between 2000' and 12,500'. From ground level to 2000' the airspace is uncontrolled. VFR traffic is allowed to operated in this uncontrolled area. VFR traffic is allowed in the controlled portion, however they must request clearence to do so.

Ok, so lets run through a scenario. Lets say you take off from Buttonville and head north. From the time you take off until you reach Highway 404 and Stouffville road (#1 on map) you will have to remain below 2500'. Technically you can go above that, but you'd have to contact Toronto Centre to request clearence into Pearsons TCA. Once you are north of #1 and you are below 2500', then you are in uncontroleld airspace. Although you dont see it on the map, the TCA ends just north of Newmarket. From that point on, uncontrolled airspace extends up to 18000'.

If you take off from Downsview and head North West, you'd have to stay below 1700' unless you want to request clearence from Toronto Centre. From listening to ATC most people request clearence to enter soon after taking off.

Let me know if I've gotten anything wrong.

Comments (2) | Permalink | Category: Air Law

Tuesday, November 22, 2005 - 22:32:23 ET

Danger Area

The rear of an airplane both in the air and on the ground is a dangerous place. In the air you have to concern yourself with wake turbulance (not caused by the engines, but the wingtip vorticies). On the ground you have to worry about Jet and Prop blast.

This "danger zone" is different depending on the type (jet/prop) and size of the aircraft. Below is the areas around an airplane where jet blast is dangerous.

A diagram is also available.

Comments (0) | Permalink | Category: Airmanship

Thursday, November 10, 2005 - 01:39:39 ET

Radio Navigation with MS Flight Sim

After reading over the chapter on radio navigation, I decided to try it out - using Microsoft Flight Simulator 2004.

I hopped in my Cessna 172, and departed Buttonville on runway 33. I climbed up to 4,000 feet and turned on the autopilot and told it to hold this altitude. First item on the list, understand how the ADF works. The ADF is a simple device that points you in the direction of the radio beacon. A simple arrow on a dial. Just turn the airplane until the arrow points straight up, now you're headed towards the NDB.
I tuned the radio to 248KHz (which was the closest NDB from Buttonville). I was surprised to hear the morse code identifier! Flight Sim rocks!

I turned the airplane into the direction until the arrow pointed straight up. I flew and flew until magically the needle swung around 180 degrees! I passed the NDB. Task one complete. The little pink icon (circle, not triangle) on the map on the leftis the NDB. You can see when I started homing in on it as my track veered to the right (east).

The next task was to use a VOR. VORs are used by everyone from private pilots to commercial airliners. They are the key to navigating the skys. I was a little confused as to how these work, since they are a little more complex than the simple NDBs. A VOR allows you to intercept it at a specific heading, called a radial. There is an indicator that tells you if you are left or right of the VOR. The idea is that you just keep the indicator centered and you will intercept the VOR at that radial.

I tuned my nav radio to 117.35MHz, the Simcoe VOR. Then I selected which radial I wanted to intercept. And flew towards the VOR keeping the marker centered. The closer you get to the VOR the harder it is to keep the needle centered. What I ended up doing was fly past the VOR then select a radial that was in the opposite direction I was going (in this case 240°) just so that I can exaggerate my track. So I started turning the aircraft until the needle was centered, then kept on flying. Once the to/from flag flipped I knew that I was on the other side of the VOR. I took a look at my heading indicator, and sure enough it showed 240°! Awesome!

I saved my entire flight in this PDF. When I decided to head north to fly past the VOR, I took the "long way" (as you can see by the little loop in the track just east of the NDB).

Comments (0) | Permalink | Category: Navigation

Sunday, November 6, 2005 - 20:28:57 ET

The Three Speeds

There are three ways of calculating your airspeed. Each one needs to be used in certain situations. It's important to know when to use which airspeed and how to calculate it.

True Airspeed: Airspeed that is corrected for air density error. This is the actual speed you are traveling through the air.
Calibrated Airspeed: Airspeed that is corrected for instrument error and position.
Indicated Airspeed: Airspeed as reported by the airspeed indicator.

To understand when and how to calculate TAS and CAS, one must understand how the airspeed indicator works.

Airspeed is the speed at which the aircraft is traveling through the air not the speed at which it is traveling over the ground (thats known as ground speed). So how does this instrument work? It measures the difference between the static pressure and the pitot pressure.

Static pressure is just pressure exerted on the instrument from the atmosphere.
Pitot pressure is the dynamic pressure created by the aircraft flying through the air plus the static or atmospheric pressure. A pitot is a little tube that allows air to enter.

Hold your hand out, palm facing your face. Static pressure is currently being exerted on your palm (the weight of the air in the room you're sitting in). Now blow on the palm of your hand - That's dynamic pressure.

Because the instrument depends on pressure to determine the airspeed, certain scenarios can cause errors in the IAS:

Density Error: As your altitude climbs, the air gets thinner and thinner. Although you are traveling at the same speed, less air molecules are entering the pitot pressure system. Therefore the pressure entering the instrument is less and therefore reports a slower speed. In order to correct for this density error you can add 2% (approx) to the IAS for every 1,000 feet of pressure altitude (I will be explaining the different kinds of altitudes later).

Position Error: This is error caused by the position of the pitot intake "hole". Eddies that are formed as the aircraft passes through the air can cause more or less air to pass over the pitot intake. Also high angles of attack (such as at take off) place the pitot intake at an unusual angle to the dynamic pressure. Take your hand again, and blow against it, however this time start changing the angle so that the bottom part of your hand is farther away from your face.. see how you "feel" less air?

So with all that out of the way.. when do you use which airspeed? In most cases you will always use TAS. To calculate TAS you need to know the altitude and outside air temp. The calculation is quite complex as it involves calculating the speed of sound (for the altitude and temperature you know). The equations can be found here. In all cases you will be calculating your TAS using your E6B.

There is one other airspeed that I neglected to mention. This is the Equivalent Airspeed. This only applys to speeds greater than 250 knots at altitudes below 10,000 feet. This airspeed takes into account the compressibility of the air. The faster you move through the air, the more compressed the air becomes just in front of the aircraft.

Comments (0) | Permalink | Category: Instruments

Tuesday, October 18, 2005 - 15:08:28 ET

VFR Flight Plans

Just discovered another difference between American and Canadian airspace rules. In the states you do not need to file a VFR flight plan regardless of where you are going. In Canada, you must file a VFR flight plan if your destination will be further than 25NM away from your aerodrome of departure.

I also noticed that Americans dont use the term aerodrome.

Comments (0) | Permalink | Category: Air Law

Wednesday, October 12, 2005 - 00:17:25 ET

Standard Traffic Circuit (Controlled Airport)

I've been reading a lot of other peoples blogs about their training. From what I gather... a lot of circuit practice happens. I keep on reading terms like "downwind leg" and "final approach", etc.. So I figured I might as well explain them to you as im sure you will need to understand at least in some part what all this means. (Canadians like to use Traffic Circuit, while the Americans call it Traffic Pattern)

The purpose of a traffic circuit is to expedite and seperate airplanes using the same airport.

The upwind side is the area on the opposite side of the landing runway from the downwind leg. Approach should be made into this area at or above circuit height. Circuit height is usually 1000 feet above aerodrome elevation (AAE)

The circuit joining crosswind is a corridor, lying within the airspace between the centre of the landing runway and its upwind end, linking the upwind side and the downwind leg.

The downwind leg is a flight path, opposite to the direction of landing, which is parallel to and at a sufficient distance from the landing runway to permit a standard rate-one turn to the base leg.

The base leg is a flight path at right angles to the direction of landing and sufficiently downwind of the approach end of the landing runway to permit at least a 1/4 mile final approach leg after completion of a standard rate-one turn to final approach.

The final approach leg is a flight path in the direction of the landing commencing at least 1/4 mile from the runway threshold, wherein an ariplane is in line with the landing runway and descending towards the runway threshold.

Comments (1) | Permalink | Category: Air Law