Saturday, August 4, 2012

Open Mouth - is Yawning Dangerous?


What do these planes all have in common?

Boeing 737 - Mangalore, India - 2010
Air Canada - April 16, 2012
Jet Blue - July 2012


The pilot woke up after a nap in the cockpit and took over the controls. His co-pilot warned him repeatedly that he was coming in at the wrong angle and that he should pull up and try again. The last sound on the cockpit recorder was the co-pilot screaming that they didn't have any runway left. The plane overshot the landing and burst into flames. Only eight people survived from 166 occupants. An investigation found the captain was suffering from "sleep inertia."

Air Canada

Several passengers were injured when the planes pilot went into a sudden dive after he mistook the planet Venus for an oncoming plane.

Jet Blue

Texas judge found that a Jet Blue pilot's bizarre ranting in the cabin was a psychic breakdown that lack of sleep was a contributing factor.

The connection in all three incidents and/or accidents was a lack of sleep. The lack of sleep isn't confined just to the airline industry. Drowsy drivers account for 20% of automobile accidents. It appears coffee, energy drinks and sleep medications have little effect on blunting drowsy people in all areas of the workplace. Industry is slowly coming around to the "brief nap" rooms that overcome sleepiness. Without that brief nap the effectiveness of the person at work is poor.

In several "posts" I wrote sleep deprivation and fatigue were covered. This is a new twist that addresses points I left out in earlier discussions.

Please read this article from todays Wall Street Journal.

Very interesting information as our schedules leave us less and less time to get adequate sleep.

Sleep deprivation is always a factor in private aviation. Don't take chances.

Thursday, August 2, 2012

Hanger Talk - Why an Airplane Spins


Usually, when you fly, and one wing drops it soon finds a force support that pushes it back up. This upward force stops the wing from going down even more. 

The other wing, by going up, reduces it own lift that, in turn,  prevents it from going up more.

It is an equilibrium effect that tends to stabilize the plane and make your day easier. 

Movement of the wing actually in motion downward causes a Relative Wind that blows upward. At the wing tip of the downward moving wing the movement of the tip is much greater than at the root of the wing. This means the upward Relative Wind is greater. (Keep in mind the Relative Wind is not coming at you - it is the wing coming at air)

When this upwardly directed Relative Wind  due to the wing going down combines with the backward directed Relative Wind caused by the forward motion of the plane, the total result is a slight upward force Relative Wind that that slows and eventually stops the wings downward motion.

Net result, whenever a wing dips down it always increases its own Angle of Attack. The increase in the Angle of Attack forces a mass of air molecules downward that results in an upward force that gently stops the downward movement of the wing. As soon as the wing stops moving down the whole effect stops. It does not tend to bring the wing up. It does not stabilize the plane by returning it to its normal condition. Basically it makes the airplane steadier, less sensitive and less ready to roll. It makes the plane easier to control.

Once the plane stalls, however, the effect reverses itself. A stalled plane is laterally unstable and the slowing of the wing downward doesn't occur. The wings Angle of Attack increases at the same time the stall happens. It doesn't find a cushion of new lift and continues to destroy even more of its lift as the Angle of Attack increases and the wing continues its downward movement.

Meanwhile the other wing continues to go up and reduces its Angle of Attack and gains more lift and wants to continue up.

A stalled plane is laterally unstable and unable to slow the movement down, of one wing, and the movement up of the other wing. The more a wing drops the more it wants to drop and vice-versa.

The plane keeps itself "stalled." This is the beginning of autorotation. If this happens on an airplane in flight centrifugal force begins to build and the different amounts of drag on the two wings creates the kind of motion called a spin.

Your instructor will teach you how to exit from a spin, prevent a secondary stall and stabilize in level flight.

Notice how Angle of Attack is prominent in this discussion.

Wednesday, August 1, 2012

Angle of Attack in Turbulent Air


What happens to an airplane when the weight (gravity) and lift force (force of air pushing the air molecules up) in equilibrium are disturbed by neither change of airspeed nor a change of the airplanes weight?

Updrafts cause a change in the angle of attack. Remember, the angle of attack is the angle at which the wing meets the relative wind. When the plane is in level flight where weight and lift forces are in equilibrium the plane is flying toward the relative wind where the angle of attack is just enough to create the equilibrium. 

The upward flowing air in an updraft (think relative wind) temporarily increases the angle of attack. The angle of attack increase creates a large surge of lift force. You feel the airplane balloon upward against your body. 

The upward motion of the airplane causes the wind of flight blow at the wing from slightly above. This produces a lower angle of attack. The lower angle of attack restores lift equilibrium. The plane, with everything else unchanged except for the updraft, resumes its steady upward flight in the updraft.


In turbulent air the plane may exit an updraft and enter a downdraft of air. The downdraft, as the air meets the wing,  temporarily decreases the angle of attack. The lift is suddenly not able to create the lift force to hold the plane up. You feel the sinking airplane  because you exert pressure on your seat belt.

The sinking of the plane causes the plane to temporarily increase its angle of attack to restore lift. It now returns to equilibrium but continues downward as long as it remains in the down draft.

Keep in mind  the attitude of the plane was always level in both the updraft and the downdraft. The airplane always seeks the flight path that that results in equilibrium between its weight and lift. The attitude of the plane remains the same but the flight path will change.

Tuesday, July 31, 2012

Maintenance Problems? Six Probe EGT and CHTG

Exhaust Gas Temperature Gauge (EGT)

Mountain Flying was a topic for the last several posts but I forgot the importance of performance enhancing steps that are safety related to all types of flying.

In the mountains a six probe EGT gauge helps you adjust your planes air/fuel mixture for top performance. 

Test each cylinder, one at a time, for its peak EGT by carefully leaning the mixture for that cylinder. After the maximum reading back off 50 degrees.

Note  each cylinders temperature. Select the cylinder with the highest temperature and back off 50 degrees. now you know, for sure that none of your cylinders are operating at a "too lean" mixture that may cause valve warp. (think expensive labor and parts cost)

You can back off just 25 degrees to lean for greatest fuel economy but you run the risk of engine overheating problems and possible damage. ( no free lunch)

On take offs at high altitude airports, if you are a flatlander, don't forget to lean out the engine for peak performance before you begin your takeoff and climb to altitude. 

Open cowl flaps, while climbing to altitude, keep the engine cool. Once on the step close the cowl flaps.

When the mixture is adjusted for sea level and you take a trip out West you may experience a fouled plug or two on your coolest running cylinders.

Cylinder Head Temperature Gauge

A major expense that faces a high performance single engine aircraft owner is finding the fouled of flawed spark plug when there are 12 plugs that a A&E needs to remove to see which one needs replacement. Thats a large labor bill.

You know what you must do before you takeoff, even in smaller power-plants in lower performance planes. Why do you run up an engine and switch from both magnetos to left magneto and back to both and then switch to right magneto before returning back to both? 

You are looking to see if all the plugs are working properly. In an aircraft engine the left magneto supplies a spark to the left cylinders upper plugs and the right cylinders lower plugs. Just the reverse for the right magneto. When the both  position for the electrical preference is selected both the upper and lower plugs are firing on each cylinder bank.

The reason for two plugs for each cylinder is safety. The RPMs will drop a slight bit if one set of plugs stops firing. Performance, of course, will suffer.

With the CHT gauge, six probe, on a high performance plane it is possible to tell an A&E mechanic the exact plug(s) to remove when you experience a "rough" engine periodically.

In flight, you can check both banks. Set the EGT and CHT to cylinder head #1. Switch from Both Magnetos to Left Magneto. When the left magneto is running alone it supplies electricity to the upper plug. If there is no drop in temperature with the left magneto running alone it means the left upper plug is okay. If you switch to the right magneto and check the EGT and CHT for cylinder head #1 and you see a discernible drop in EGT and CHT it may mean the  lower plug on the cylinder #1 is fouled, flawed or cracked.

You can continue to test each cylinder in this manner. If you detect a change in EGT and CHT for another cylinder note which plug isn't operating properly and report those plugs to your mechanic. 

Net effect is vastly lower cost and your peace of mind.

Sunday, July 29, 2012

A Few Mountain Facts to Store Away

Adiabatic Lapse Rate The temperature the air drops per 1,000 feet of altitude - 4.5 degrees F.

Density Altitude The actual density of the ai,r at the place of observation, rather than from the ground.  An increase in the temperature, and to a lesser degree, the humidity (because the water content will displace air) causes an increase in density altitude. The density altitude in  hot and humid conditions, is significantly  greater than the true altitude.

Minimum Requirements for Mountain  Flying a basic course in Mountain Flying and minimum HP of the engine is 160 H. Add 60 HP for each additional occupant to the original 160 HP to insure adequate performance in the mountains.

Pass Clearance and Visibility 1,000 Ft and 15 miles
Winds Aloft - 25 knots or better may include turbulence at mountainous altitudes

Pressure systems Interpret the location of high pressure systems (clock-wise air circulation and low pressure systems (counter-clockwise air circulation) for wind aloft velocities in flight planning

Energy Released in Cloud Formation Ice formation in clouds. Each gram of water releases 540 calories when it changes state from liquid to ice. Thunderstorms build when heat is released from that formation.

Temperature  Inversions Warm air on top of cold air causes the formation of fog when the temperature/dew point spread is zero.

Increasing Plane Performance Reduce your plane weight to 90% of maximum gross weight. This will your plane to return to near normal performance for rate of climb and ceiling.

Aspirated Engines Lose 3% of power per 1,000 feet gain in altitude. Think of a propeller as a vertical wing. The prop loses "pulling power" with altitude gain.

Turn Radius Anticipate the turning radius to increase with increases in altitude.

Routes Learn to follow rivers, roads, low valleys to reach your destination. Direct routes may involve very mountainous weather and performance limitations.

Radio Frequencies Weakness and location are safety checks.

Mixture Lean at altitude to prevent spark plug fouling.

Canyons Fly close to mountains to take advantage of updrafts for altitude gain.

Turbulence and Downdrafts Turn 90 degrees away from a ridge creating turbulence and fly away until it dissipates.

Weather Mountains move moist air quickly. Keep looking for changes. Safety first.

Oxygen Tanks full? Tanks for passengers.

Route Change Divert if conditions become dangerous.

Emergency Locator Beacon Working?

Crashes Stay with the plane.