Preparation for your Practical Test

Flight Instructors do a very good job teaching their students the intricacies of flight and good aeronautical decision making.  These instructors spend countless hours analyzing how well their students are performing both in their knowledge of aviation and ability to perform with the practical standards.  Only when the instructor feels the student is ready and all aeronautical experience requirements are met, will he allow them to apply for the practical test to earn their new privilege.

One of the keys to this preparation is the Practical Test Standards.  If you haven’t seen this document yet while going through the preparation for the practical test, you need to take a look at it.  This really is the cheat sheet on what the examiner is required to test on; everything from your aviation knowledge, to ability to fly the airplane, to other special areas of emphasis.

How many of the instructors have gone through the front sections of the PTS to show them what it means when a maneuver is acceptable to the examiner or when the examiner is forced to issue a notice of disapproval.

When I was going through my training back in the day, I wasn’t told about the boundaries the examiner has to stay within.  I was under the impression, they could pass or fail a student for anything they wanted.  I was on both the good end and the bad end of that.  Thinking back, there were some maneuvers that I completed that were well within the PTS standards and the examiner failed me while some were not and he didn’t say anything.  If I knew now back then, I would have had a leg to stand on when I disagreed with his decision.

Let’s take a look inside the PTS book to see what it says.  In the Introduction section, one of the very first things it says is that “Adherence to the provisions of the regulations and the practical test standards is mandatory for the evaluation of private pilot applicants.  On page six of the introduction, under the heading Use of the PTS tells the applicant they are required to be evaluated in ALL areas of the PTS, unless otherwise noted (the only PTS that allows this is the CFI PTS… that I know of). 

Page nine lists the responsibilities of the flight instructor.  If your instructor cannot give you the experience and aeronautical knowledge necessary in all areas of the PTS, it is time for a new instructor.  They are required to emphasize your performance in effective visual scanning, collision avoidance procedures, manufacturers procedures and special emphasis areas. 

Page ten lists the examiner responsibility during the practical test.  They are required to determine if the applicant meets the acceptable standards of knowledge and skill of each task with in the PTS.  If something goes wrong, the examiner may require the applicant to repeat the task in the interest of fairness although the examiner has the option to not allow a repeat of a task.

The heart of this blog is the next two sections. 

Satisfactory performance is defined by five things.

1. Perform the Tasks specified in the Areas of Operation for the certificate or rating sought within the approved standards
2. Demonstrate mastery of the aircraft by performing each Task successfully
3. Demonstrate satisfactory proficiency and competency within the approved standards
4. Demonstrate sound judgment and exercises aeronautical decision making / risk management
5. Demonstrate single pilot competence if the aircraft is type certificated for single pilot operations.

Unsatisfactory Performance is defined as these four things

1. Any action or lack of action by the applicant that requires corrective intervention by the examiner to maintain safe flight
2. Failure to use proper and effective visual scanning techniques to clear the area before and while performing maneuvers
3. Consistently exceeding tolerances stated in the objectives
4. Failure to take prompt corrective action when tolerances are exceeded

I really like number three and four.  In the many practical tests that I have taken apart in, the examiners expect nerves to play a part in the applicant exceeding the tolerances.  If the applicant exceeds them once and promptly corrects, it is not a failure.  If it happens twice, probably not.  Three times and you are starting to show consistent behavior to fly outside the standards and that would be unsatisfactory.  Lets take steep turns as an example, you roll into a 45 degree bank and forget to pull back on the yoke, you descend fairly quickly 150 feet below your assigned altitude.  If you stay there, it is a bust; but if you promptly correct and get back within standards it is OK.  If it happens again, well you are starting to show consistency. 

I’ve talked to many pilots who were stressed out over wondering what is acceptable or not to the examiner and what happens if they get outside of standards only once.  The answer is nothing.  The examiner will most likely pass you.  The criteria used is consistency and a lack of prompt corrective action.  The other good thing about the introduction to the PTS it clearly states that the tolerances are established for a good flying day.  If there is a lot of turbulence, you won’t be held to the same standard as when the air is calm.

Hopefully this takes some of the pressure of making yourself perform at your best.  That pressure may make you fly worse than before.  My advice, relax you know what to expect from the examiner and treat them like your very first passenger.

How True are We?

We all know that as we climb higher into the atmosphere the indicated airspeed will not change while the true airspeed will increase.  This is a known feature of climbing higher.  What may be unknown is that at a certain range of altitudes the true airspeed will no longer increase but slowly decrease.  Why is that?

First, to prove the point take a look at a performance chart for a standard business jet.

Notice how the true airspeed slows down as the altitude is increased.  The other piece of information not listed on this picture is the aircraft is cruising at a constant Mach number.  The Mach number is a ratio of airspeeds where the current true airspeed of the aircraft is divided by the speed of sound.  The interesting thing about the speed of sound is that the speed is directly related to the temperature of the surrounding air.

One of the characteristics of our atmosphere is different temperature rates in the parts of the atmosphere.  For example, the troposphere we currently live in has a temperature lapse rate of around 2 degrees per thousand feet.  The troposphere extends from the surface of the earth to around 25,000 to 35,000 feet depending on the season of the year and latitude.  The tropopause is right above the troposphere and is characterized by a constant temperature.  This is where most corporate jets fly.  In the example above, the tropopause starts at FL360.

So what is happening with the chart above?  The answer lies in how the true airspeed interacts with the Mach number.  As the airplane climbs, at some point the crew will transition from using indicated airspeed to Mach speed.  Depending on the aircraft, that altitude may be different but almost always above FL250.  Our original premise that true airspeed increases with altitude is absolutely correct but what is now changing is our indicated airspeed.

For our aircraft to fly at a constant Mach number, the airplanes indicated airspeed will decrease with altitude.  The chart to the left shows an aircraft who is climbing at 300 knots indicated airspeed until the aircraft reaches .81 Mach at FL320.  Above this altitude the airplane continues to climb at .81 Mach till reaching FL500 (which is higher than most aircraft fly).  We can plainly see that our indicated airspeed decreases and that is the reason why our true airspeed decreases just a little bit before stabilizing at 465 K.

What about those air temperatures?

As you get farther along into your flying career, you will most likely find gauges for different types of air temperatures.  You are probably thinking, what all I need to know is one air temperature but that really isn’t true.  For some reason, aircraft manufacturers have used separate air temperatures  as the basis for their calculations in the performance charts.

For example, the early Learjet aircraft, 20 series, used a ram air temperature (RAT) gauge while later model Learjet aircraft use static air temperature gauges (SAT).  Bombardier Challenger 604 aircraft use true air temperature (TAT) in their calculations as well as SAT readings.

What do all of these things mean?

• Outside Air Temperature (OAT): The free air static temperature obtained from either ground meteorological  sources or from inflight temperature indications adjusted for instrument error and compressibility effects
• Static Air Temperature (SAT):  The total air temperature obtained from onboard temperature measurement adjusted from compressibility effects.  (Inflight SAT is equal to OAT.)
• Total Air Temperature (TAT):  Static air temperature plus adiabatic compression (ram) rise.
• Ram Air Temperature (RAT):  The static air temperature corrected for full adiabatic compression rise corresponding to the true Mach number, and multiplied by a recovery factor.

Confused yet?  Each of these definitions rely on a previous definition creating a circular definition that doesn’t really answer anything.  Though a search of the web doesn’t really give us a better definition.  Also unfortunately for us, these definitions come from multiple airplanes.

This is what I know.  OAT is always reported by the ground station.  As the airplane takes off, the temperature of the air (where it is measured) rises due to adiabatic compression.  The onboard computers will either directly report that value (as in the case of older airplanes) or will convert the RAT or TAT to SAT and display that value to the pilot.  This provides one consistent temperature for the pilot.  The chart below will convert a RAT scale to a SAT/OAT scale.

There are times where knowing the TAT or RAT is preferred and that mostly comes when the aircraft enters icing conditions.  If you take a look at the Mach number and RAT gauge you will notice an increase in RAT value with an increase in Mach number.  Meaning the faster an airplane goes, the hotter the air temperature.  Remember watching Apollo 13 when the capsule was coming back into the Earth’s atmosphere.  The temperature was so hot they were worried that the heat shield would fail. 

How does this help with icing conditions?  Well… a wise old friend of mine told me once that if you ever get into icing conditions the best thing to do after turning on any anti-ice / de-ice equipment is to keep the speed up.  The faster you can go the easier it is to get rid of the ice on the airplane.  He then lamented, that the 250K speed limit under 10,000 FT MSL doesn’t really help matters in icing conditions.  Here is another chart that graphically shows what the table above displays.