Spring Rains and Wet Runways - Beware!

It doesn't take much water on the runway to turn an airplane temporarily into boat!  That's because of a unique phenomenon called "dynamic hydroplaning."

Dynamic hydroplaning is a condition in which the airplane tires ride on a thin sheet of water rather than on the runway’s surface. Because hydroplaning wheels are not touching the runway, braking and directional control are almost nil.

Tire pressure is a factor in dynamic hydroplaning. By the simple formula shown in the adjacent graphic, we can calculate the minimum speed, in knots, at which hydroplaning will begin.

In plain language, the minimum hydroplaning speed is determined by multiplying the square root of the main gear tire pressure in pounds per square inch (p.s.i.), by nine.  For example, if the main gear tire pressure is at 36 pounds per square inch, the airplane would begin hydroplaning at 54 knots.

Landing at higher than recommended touchdown speeds exposes the airplane to a greater potential for hydroplaning.  Once hydroplaning starts, it can continue well below the minimum, initial hydroplaning speed.

When the runway is wet, anticipate braking problems well before landing and be prepared for hydroplaning.  Select a suitable runway most aligned with the wind.  Mechanical braking may be ineffective, so aerodynamic braking should be used to its fullest advantage.

Losing it the last minute on the ILS!

Not surprisingly, the most challenging part of any instrument flight is often the final approach to landing.  And the most demanding portion of the final approach is the last couple hundred feet to the decision height (DH) or missed approach point (MAP).   When mistakes are made here, the outcome is often tragic.

In February, 2005, a 395 hour, instrument rated pilot flying a Columbia 400, with three passengers aboard, lost it right at DH last year while attempting an ILS approach to minimums at the Stafford Regional Airport in Virginia.

All four people perished in the accident.

Could Fatigue have been a factor?

As is often the case, the accident occurred at the end of what was probably a long day for the pilot.  They had been returning from a night basketball game in Winston-Salem, NC.  The weather along the route was IFR.  

Their originally intended destination was the Fredericksburg-Shannon Airport in Virginia.  After flying the GPS approach to this airport and executing the published missed approach procedure, the pilot called Potomac Approach and requested to be re-cleared to the Stafford Regional Airport. 

Weather at Stafford was no better than at Shannon, but they have an ILS procedure with a 200' decision height.  So far, so go.  The decisions were correct. 

The only thing working against the pilot, other than the weather, was his possible fatigue.   As a low time pilot operating a sophisticated airplane,  he had his hands full.  In any case, he was cleared for the ILS Runway 33 approach to Shannon.

According to the NTSB report, things we going along fine as the aircraft intercepted the localizer and slithered down the glideslope.  According to the FAA's recorded radar track, the pilot was on the localizer right down to 300' above the airport elevation.  Then he apparently lost it!  The airplane hit trees 300 yards to the left and about 3/4ths down the 5,000' runway. 

Weather - "Misty and nasty"

Unfortunately, without the infamous black box and cockpit voice recorder, we will never know what actually transpired in the cockpit during the final seconds before the crash. 

One area that has been a constant concern to me with low time pilots flying sophisticated airplanes is their dependence upon the autopilot to fly instrument approaches.

In this fatal accident scenario, had the pilot been flying an autopilot coupled approach, he would have had to "kill" the autopilot shortly before or upon reaching the decision height.  An immediate transition to "hand flying" would then be required to either land or fly the missed approach procedure.

Again for emphasis, we have no clue about what actually transpired on this fatal flight, but had the pilot fumbled only a split second in this fast airplane when transitioning from autopilot to hand flying while descending down through 200'AGL (or less), he could easily find himself in the trees! 

Lessons learned . . .

In summary, there are dozens of things that can complicate our proficiency when flying an instrument approach to minimums.   Proper planning and approach preparation is the key to success! 

NTSB Report

Pitch vs. Power

If you want to light a fire under a group of pilots, try tossing the pitch vs. power subject into the conversation.  The result will be an exchange of circuitous logic where neither side of the debate wins or loses.

When descending down the ILS, for example, the question will be, "Do I set the power, then alter pitch to keep me on the glideslope (GS)?"   Or, perhaps, "Do I set the pitch then, then alter power to keep me on the GS?"

The answer is . . . BOTH!

Let's say our objective is to remain firmly centered on the GS (as it should be).  Should we drop below the GS, we can increase pitch which, of course, will cause our airspeed to reduce.  When airspeed drops, lift is reduced.  This means we must add power to increase airspeed.  As the aircraft speeds up, lift is increased.

To keep from climbing above the GS, we must lower the pitch to reduce the angle of attack. 

If we want the aircraft to decelerate while remaining on the GS, power must be decreased.  As the aircraft slows down, lift is reduced.  Then we must increase the pitch in order to increase the angle of attack.

The reverse is also true.  If we want to increase airspeed while on the GS, power must be increased to overcome drag.  As the aircraft speeds up, lift is increased.  Then we must decrease pitch in order to decrease the angle of attack.

Clearly, then, the most precise method of controlling flight path is to use pitch and power to remain on the GS at the desired airspeed.

And we wonder why the pitch vs. power debate continues.  The truth is, power and pitch are inter-related when it comes to remaining on the GS.  One without the other simply will not work.

Keeping the Spark Alive!

The mag check is as basic to piston engine flying as is looking into the mirror before leaving home in the morning.   It is a ritual seldom ever forgotten by even the most careless pilot.  But what we are really looking for when we perform this mag check . . . and why?

What are we looking for?

It is fairly common knowledge, even among beginning pilots, that each cylinder in a piston engine has two sparkplugs . . . for two reasons.   One reason is for improved combustion;  the other is for redundancy.

In addition, there are two independent magnetos that send electrical impulses to the sparkplugs.  These electrical impulses create the spark that ignites the fuel in each cylinder.

One sparkplug from each cylinder is connected to the right magneto and the other sparkplug is connected to the left magneto.  Both magnetos are "ON" during normal operation.

What to look for in the mag check . . .

Engines operate more efficiently with two sparkplugs igniting the fuel/air mixture in each cylinder.  Under normal circumstances, we will see a 50 to 75 RPM drop when we turn off either the right or left mag.

What to do with an abnormal mag check

Like so many other things in aviation, it depends!  An excessive RPM drop is the most common abnormal response to a mag check.  This is typically an indication of one or more fouled plugs.  Aggressive leaning during the high RPM run-up will occasionally solve this problem.

If the engine runs normally on either mag after this lean run-up, we should be good to go.  Be sure, of course, to switch on BOTH mags before launching.

What if we get no RPM drop?   Hmmm. . . likely this means that the "P" lead to one or the mags is broken.  This can be confirmed by turning the ignition switch to "off."  If the engine continues to run, it's likely the "P" lead.  Get it fixed before launching.  

Lastly, what if the engine quits when we switch to either mag?  This is a sure indication that the mag we switched to is bad.  Obviously, DON'T fly!

A word or two about doing engine run-ups . . .

I was standing on the ramp of a neighboring airport on a cold morning recently when a flight instructor and student boarded a Piper Arrow.  I heard the word "CLEAR," followed by engine start. 

Almost instantly, I heard the engine accelerate to high RPM as the CFI was apparently demonstrating how to perform a mag check.  "Ouch," I said to myself.  Instead, this was a lesson on how to abuse a cold engine!

Second, I watched people walking behind this airplane grab their hats and coats as ramp dust and debris was blown across their path!

The message here is simple.  Engine run-ups and mag checks should never be performed on COLD engines.  Instead, allow sufficient time for the oil temperature to rise into the "green" on the gauge or at least 100d F.

Next . . . perform engine run-ups and mag checks ONLY in designated run-up areas.  If none are indicated, taxi close to the departure runway and perform them there.

In summary, piston engines require three elements to operate: (1) fuel; (2) air; and (3) a spark.  Properly diagnosing our magneto system is a basic requirement of safe flight.

Night Currency . . . more than a legal requirement!

Has it been a while since you have done any night flying?  Day and night, it's all the same, right?   Maybe yes, maybe no.  Like so many other aspects of aviation, it depends.

For example, let's take a sophisticated single like a Piper Cherokee Six.  Pile in three friends and fly to a nearby airport for dinner.   Do you see any problem so far?   Weather you ask?  VFR.   This flight had all of the makings of a wonderful evening of enjoyment on this September 10th evening in 2005.

The missing pieces

Now let's fill in the missing pieces.  First, the big piece.  The pilot had not flown at night at any time in the previous 16 years.  In fact, the pilot had only logged a total of 7 hours in the previous 16 years!  Those 7 hours were received 2 months earlier as part of an insurance checkout on his recently purchased Piper Cherokee Six and an biennial flight review (BFR) that was included as part of that checkout. 

Back to the flight . . .

Winds on the evening of this flight were reported at 130 degrees at 3 knots;  visibility was 6 miles with haze;  the sky was clear and the temperature was 23 degrees Celsius and dew point 17 degrees Celsius.  According to the U.S. Naval Observatory, 41-percent of the moon's visible disk was illuminated.

The flight began in Rochester, Indiana at 8:40pm of September 10, 2005.  The pilot and three friends were returning to their home base in Wabash, Indiana from an earlier flight they made that afternoon to Rochester, Indiana for dinner.

They arrived back over the Wabash Municipal Airport (IWH) 20 minutes later (9:00pm).  Note:  Sunset occurred at this airport at 7:00pm and the end of civil twilight was 7:28pm.

NTSB Report

Turning around!!

The annals of aviation history are filled with accounts of pilots attempting a 180 degree turn, then running into something hard . . . like the side of a hill, mountain, or building.

The most notable recent event of this kind occurred in New York City last October when NY Yankee pitcher Cory Lidle and his flight instructor attempted a 180 degree turn over the East River in New York City.

The question in all such cases is, "How wide will the turn be in terms of lateral feet?"

The answer to this question, of course, depends upon three factors:  (1) airspeed; (2) bank angle; and (3) winds.

Airspeed:

Looking first at airspeed, as the illustration below shows, the radius of any turn increases as airspeed increases (assuming constant bank angle).  This fact can easily surprise pilots who transition to high performance airplanes. 

Reader note:  The following two paragraphs were changed on 3/31/07 to reflect corrected turnaround distances.  Thanks to eagle-eyed OTA reader, Thom Riddle who first pointed out the error and thanks to Keith Harlock who re-computed the correct turnaround distances.

A Cessna 172 flying at 100 knots will require a 3,000' (2x radius) wide turn when banking at 30 degrees to complete a 180 degree turnaround.   A high performance airplane flying at 200 knots, while in the same 30 degree bank angle will require more than four times the lateral distance or 13,000' to make the turn!  

Bank Angle:

Now take a Cirrus SR20 flying at 150 knots.  A 180 degree turn can be accomplished in 4,000' at a 45 degree bank angle.  Reducing that bank angle to 15 degrees increases the turn width four times - to 16,000'.

Circling Approaches - The good, the bad, and the ugly!

Mention circling approaches to a group of hardened instrument pilots and you'll hear a lot of debate.  Depending upon circumstances, points of view will range from "useful" to "deadly." 

Many operators including some airlines prohibit their pilots from conducting circling approaches under certain circumstances, particularly at night.  Curiously, however, circling approaches can be a safer alternative to making a downwind or even a crosswind landing. You just have to play by the rules!

A quick review . . .

Circling approaches are used anytime the final approach segment of a published approach procedure is aligned more than 30 degrees from the runway heading.  Such instrument approaches have an alpha character in the approach title rather than a runway number, e.g., VOR-A approach.

Circling approaches are also used because of winds, to land on some runway other than the one for which an instrument approach procedure (IAP) has been established.

Size of the Circling Area around the airport

The published circling minimums for any airport affords us a minimum of 300' of obstacle clearance anywhere in the protected area.  The size of this protected area is defined by the approach category of the landing aircraft as illustrated in the chart (left).

The key in performing a circle to land maneuver is to remain far enough away from the landing runway so that no unusual flight attitudes or maneuvers are required to land.  

In low visibility, however, we need to remain close enough to the landing runway so as to not lose sight of it!

Now for the good, the bad, and the ugly . . .

More information regarding this accident.

Solving the Mystery of "YAW"

With automatic transmissions coming standard on nearly every automobile on the market today, one wonders just how many of us can drive "stick?"

The same can be said about late model production GA aircraft.  While none come equipped with automatic transmissions, many of them require little or no rudder input to perform a coordinated turn.  This, of course, begs the question, how many of us use our rudder pedals effectively?

Why rudder?

Ask any flight student what the rudder is for and he or she will give you the stock answer:  "To correct for adverse yaw."

Next question . . . what is adverse yaw and how is it caused?

Now the answer is a bit slower in coming.   "Ahhh . . . adverse yaw is caused by . . .  Hmmm, I'm not really quite sure."

What is Adverse Yaw?

Adverse yaw is the turning of the airplane about its vertical axis as depicted in the illustration (right).

When turning right, for example, we cause the aileron on the left wing to deflect downward.  This causes the left wing to lift. 

As with all lift, induced drag is an undesirable by-product.  This added induced drag on the left wing attempts to yaw the airplane’s nose in the direction of the raised wing (left in this case). 

In addition, the lowered aileron on the left wing produces more parasitic drag than the raised aileron on the right wing.  This, too, yaws the nose to the left in a right turn.

So how do we counteract this yawing force to the left as we make a right turn? 

Answer:  The rudder (of course)!

Applying aileron pressure is necessary to
place the airplane in the desired angle of bank, while simultaneously applying rudder pressure to counteract the resultant adverse yaw.

The amount of rudder control required is greatest at low airspeeds, high angles of attack, and with large aileron deflections.  However, with lower airspeeds, the vertical stabilizer/rudder combination becomes less effective, and magnifies the control problems associated with adverse yaw.

Also More Elevator . . .

During a turn, the angle of attack must be increased by applying elevator pressure because more lift is required than when in straight and level
flight. The steeper the turn, the more back elevator pressure is needed.

As the desired angle of bank is established, aileron and rudder pressures are relaxed.  This stops the bank from increasing because the aileron and rudder control surfaces will be neutral in their streamlined position. Elevator pressure is then held constant to maintain a constant altitude.

Factory to the Rescue!

Our good friends at the factory have helped to reduce the effects of adverse yaw by designing features into the design of some of their aircraft. 

Differential ailerons is one such feature.  Here, the up moving aileron creates more of a deflection than the down moving aileron.  This serves to "balance" the parasitic drag described above.

A rudder/aileron inter-connect system is another way manufacturers have helped to reduce adverse yaw.  As we apply aileron pressure to bank, the inter-connect system automatically applies rudder pressure in the same direction.

In summary, achieving coordinated flight and keeping the ball in the inclinometer centered does more than keep your flight instructor happy.  It WILL prevent an inadvertent spin!!!!  Remember, a spin results from an uncoordinated stall!
 

"Not-So-Quiet-Birdmen" Dine in Style!

Every pilot has a sacred obligation to keep the spirit of aviation alive and well.   This occasionally involves ritual eating and drinking, boisterous tales of aerial heroism, and shared secrets never before discussed in open forum. 

A growing group of Buffalo-area aviators are doing their best to promote the spirit of aviation in an informal group they formed about six months ago called the "Not-So-Quiet-Birdmen." 

OTA readers are invited to share their example by forming "NSQB" chapters in their own communities!

Note:  Any connection with the highly respected "Quiet Birdmen" (QBs) organization is purely coincidental and unintended!

Every flight instructor knows that FAA knowledge tests are riddled with outdated questions that address useless trivia that have no bearing on the safety of flight in today's national airspace system.  The old black and white radar summary charts, for example, haven't been used by the U.S. Weather Service since the 1980s.  Yet there are multiple questions on these relics of an earlier age on every knowledge test from private pilot to ATP.

Meanwhile, NEXRAD images are depended upon by thousands of GA pilots to make critical go/no go decisions.  They view these images on their computers, on their cell phones, and on portable and panel-mounted GPS units.   How many knowledge test questions address NEXRAD interpretation and limitations?  None!

Flight students spend endless hours working through ADF and RMI orientation questions while the FAA is decommissioning these hold-overs from the 1940s and 50s.  Meanwhile, knowledge tests are devoid of the legal ramifications of using handheld GPSs to navigate through controlled airspace.

This problem isn't going to be fixed any time soon.

Let's face it.  Updating the airman knowledge tests (and the PTS) would have a profound effect on what all GA pilots know and do.  While it makes absolute sense to fix this problem right now, the FAA appears focused upon other priorities.

No, Virginia, the airman knowledge tests are so far down the flag pole that they will not be saluted by the FAA until the polar ice cap totally melts. 

So what should we be doing about it?

Ultimately, it is the flight school and/or flight instructor that sets the pace of learning for every pilot under his or her tutelage.   All of us wants to be sure that each student is equipped with the knowledge and tools that will enable him or her to operate safely in today's national airspace system. 

To burden students with knowledge and tools they will NOT need or use is, frankly, a gross waste of the students' time, money, and patience.   Granted, picking and choosing what students need to know to pass the various tests is something that we CFIs cannot do.  But we can place emphasis on knowledge elements we deem more important than others. 

Given the enormous challenges facing today's GA pilots, radar summary charts and ADFs are not high on my list of flight safety priorities.  The sooner the FAA addresses this issue, the easier my job will become.  More importantly, the safer our  pilots will become!