Its snowing out right now, and I can't go flying. Flying in the wintertime has both its pros and cons. Airplanes love cold air. Cold air is more dense, which allows the engine to produce more power. The dense air also provides more substance for the propellers and wings to displace, thus giving more thrust and more lift. In the Cessna 150 these effects are most visibly seen during a climb. On a hot summer day with just me in the airplane I can expect around a 3-400 ft/per min climb, whereas in colder winter weather I've see climbs upward of 600 fpm.
Winter flying also requires more cautious actions to avoid airframe icing. Airframe icing is defined as the buildup of ice on the wings and other surfaces of the aircraft, which can add weight to the airplane as well as reduce lift. In icing conditions, ice most heavily builds up on the leading edges of the wings and other surfaces of the airplane. Ice on the windscreen can impede forward visibility from the cockpit. More importantly, icing on the wings, if appropriate action is not taken, can actually bring an airplane down. The ice changes the shape of the wings, which alters how the air flows over it. This can reduce the amount of lift the wings produce.
All of the larger airliners have equipment to defend against icing, and many smaller aircraft have systems as well. There are 3 different types of ice protection systems, categorized into two different groups: De-icing, which is to remove ice that has already built up, and Anti-icing, which works to prevent ice buildup in the first place. De-icing boots are strips of rubber that are glued onto the leading edges of the wings and other flying surfaces. When ice accumulates on the boots, they can be inflated with air which breaks away the the ice so it falls away. This is by far the most common system employed on smaller business jets and piston planes. Less commonly seen is the weeping leading edge system. Like on the Cirrus line of private aircraft, the leading edge has a grid of tiny holes covering the entire leading edge. When activated, these 'pores' seep anti-icing fluid, which is spread by the airflow over the wing. This fluid prevents water droplets from freezing on the wing. Lastly, and only used on jet aircraft, is the hot-wing anti-icing system. The leading edge is heated from bleed air from the jet engines, which prevents icing from freezing onto the leading edges.
Neither of the airplanes I fly are equipped with de-icing, or anti-icing systems. Additionally, neither aircraft perform particularly well with ice, compared to other airplanes. The Cessna 150 is a very small, underpowered airplane. Do to the lack of power, it would not be able to handle the extra weight and decreased lift as well as more powerful airplanes could. The Twin Comanche, though having lots of power, has what is called a laminar flow wing. Simply speaking, it is critical for this type of wing to have a very smooth surface, free of any contamination. Ice on this wing would change the flow of air very drastically. This means that I have to be very cautious as to the weather conditions I fly into, and as such, I am not going flying today.
Thursday, December 7, 2006
Wednesday, December 6, 2006
Landing a Twin
Well here is my post on landing the twin as promised. Hopefully I haven't lost too many people to confusion or boredom from the last post. I promise the next one will be less technical.
So here we are, screaming along in our twin. We've been cleared to the downwind, so now we're flying parallel to the runway in the opposite direction, at circuit altitude, which is 1000 ft above the airport. If we haven't already we'll pull the power back to around 17 " of Manifold Pressure, which is about half power, so we can slow down. We'll let our speed bleed off a little. Now we need to get our pre-landing check done. Mixtures go to full rich, fuel selectors should be on main tanks, electric fuel pumps on, and once our airspeed has dropped below 150 mph, we can drop the landing gear, and we'll watch for our green light, indicating the gear is down and locked. The gear will be slowing us down even more, so now once we're below 125 mph, we can lower the flaps.
At this point, we'll be ready to turn onto our base leg, which is 90 degrees to the runway. We slow down to our initial approach speed which will usually be 120 mph, unless we're following in a slower plane and we need to go slower to give them more spacing. Soon enough we'll be ready to turn onto our final leg, lining us up with the runway. I have to remember to not wait too long to turn, otherwise I'm going to turn too late, and have to do an S turn to get ourselves lined up again with the centreline. This isn't a Cessna 150 and it won't turn on a dime as I'm used to. Final approach speed will be 110 mph. Once we're established on final we do our G.U.M.P. check. G.U.M.P. is an acronym for Gas, Undercarriage (landing gear), Mixtures, and Propellers. This means we want to double check that our fuel pumps are on, and fuel selectors on the main tanks, our undercarriage is down and locked (belly landings are quite exciting I hear but not very cost-effective), Mixtures are rich, and Propellers are full forward. All this, with the exception of the landing gear, doesn't really matter a whole lot for landing, but we want to be already set up to climb out if we have to overshoot for whatever reason. So as long as we've been cleared to land we're good to go. All we have to do is fly the airplane down over the threshold, slowly retard the throttle and flare (raise the nose to bleed off our airspeed and touch down on the main wheels).
The flare I find is a much smaller angle in comparison to a Cessna 150 or 172. The airplane is travelling faster and needs more time to slow down and settle onto the runway. I initially had problems flaring too much, and the airplane would zoom up, bleed off its airspeed, and then drop onto the runway - hard on the airplane and it does a number on your back too! All we need is just a very slight nose up attitude and hold it there until our airspeed decreases and the airplane settles onto the runway. Once we've got all three wheels onto the runway its just a matter of applying the brakes and stopping straight ahead. Onto the ground once more safely and uneventfully, just the way we like it!
So here we are, screaming along in our twin. We've been cleared to the downwind, so now we're flying parallel to the runway in the opposite direction, at circuit altitude, which is 1000 ft above the airport. If we haven't already we'll pull the power back to around 17 " of Manifold Pressure, which is about half power, so we can slow down. We'll let our speed bleed off a little. Now we need to get our pre-landing check done. Mixtures go to full rich, fuel selectors should be on main tanks, electric fuel pumps on, and once our airspeed has dropped below 150 mph, we can drop the landing gear, and we'll watch for our green light, indicating the gear is down and locked. The gear will be slowing us down even more, so now once we're below 125 mph, we can lower the flaps.
At this point, we'll be ready to turn onto our base leg, which is 90 degrees to the runway. We slow down to our initial approach speed which will usually be 120 mph, unless we're following in a slower plane and we need to go slower to give them more spacing. Soon enough we'll be ready to turn onto our final leg, lining us up with the runway. I have to remember to not wait too long to turn, otherwise I'm going to turn too late, and have to do an S turn to get ourselves lined up again with the centreline. This isn't a Cessna 150 and it won't turn on a dime as I'm used to. Final approach speed will be 110 mph. Once we're established on final we do our G.U.M.P. check. G.U.M.P. is an acronym for Gas, Undercarriage (landing gear), Mixtures, and Propellers. This means we want to double check that our fuel pumps are on, and fuel selectors on the main tanks, our undercarriage is down and locked (belly landings are quite exciting I hear but not very cost-effective), Mixtures are rich, and Propellers are full forward. All this, with the exception of the landing gear, doesn't really matter a whole lot for landing, but we want to be already set up to climb out if we have to overshoot for whatever reason. So as long as we've been cleared to land we're good to go. All we have to do is fly the airplane down over the threshold, slowly retard the throttle and flare (raise the nose to bleed off our airspeed and touch down on the main wheels).
The flare I find is a much smaller angle in comparison to a Cessna 150 or 172. The airplane is travelling faster and needs more time to slow down and settle onto the runway. I initially had problems flaring too much, and the airplane would zoom up, bleed off its airspeed, and then drop onto the runway - hard on the airplane and it does a number on your back too! All we need is just a very slight nose up attitude and hold it there until our airspeed decreases and the airplane settles onto the runway. Once we've got all three wheels onto the runway its just a matter of applying the brakes and stopping straight ahead. Onto the ground once more safely and uneventfully, just the way we like it!
Tuesday, December 5, 2006
Flying a Twin
Recently I started training for my Multi-Engine Class Rating, in our newly christened 1964 Piper Twin Comanche. My first flight was quite the shock going from the ambling pace of a Cessna 150 straight to the high speed, high demand cockpit of a complex twin. So I am excited to review what I have learned so far.
Just a heads up, this is going to be a fairly technical post, so those not interested in reading procedures and what-not, sorry. Otherwise read on!
For those of you out there who know what a Constant Speed Propeller is, feel free to skip these next two paragraphs, I just feel compelled to give a little background knowledge to those unaquainted with the complex aircraft.
First of all the term "Complex Aircraft" generally refers to an aircraft with retractable landing gear and a constant speed propeller, or in my airplane's case, propellers plural. A constant speed propeller is one where you can control the pitch of the blades. This gives you an advantage similiar to different gears in a car. A fine pitch in the propeller, similiar to a low gear, will give us lots of torque for the take-off and climb, whereas a coarse pitch, like a high gear, will give us a fast cruising speed.
In addition to a power control (controls amount of air aloud into engine) and mixture control (controls amount of fuel aloud into engine) we have a a set of Propeller controls. These don't directly control the pitch of the propeller blades, but actually control a governor that allows the blades to change their pitch in order to hold a constant engine RPM as directed by the prop controls. Hence the name "constant speed propeller". The governor, based on how much power is being delivered to the props by the engine, will adjust the pitch of the blades to either slow down, or speed up the engine as needed to maintain the set RPM. For example. Say we want to set our props to a cruise setting, and right now we have just finished our climb and are in a fine pitch climb setting of 2500 RPM. We will pull back the prop control levers until the Tachometer reads our desired RPM, which we will call 2300. The governor senses that right now the props are spinning at a faster rate then 2300, so it increases the pitch, which in turn loads the engine and slows it down to 2300. If we were to increase the power being delivered to the props by pushing our throttle forward, the props will naturally want to speed up, so the governor will once again increase the pitch of the props in an attempt to keep them spinning at 2300 RPM. So unlike a fixed pitch prop aircraft where power to the engine is measured on the Tachometer, we measure power from the Manifold Pressure Gauge, in Inches of Mercury, and we manage the prop settings using our Tachometer.
Now that we have a little background knowledge, I can talk about the procedures we use for taking off.
For taking off we use a full fine pitch setting for the props, full power to the engines, and no flaps. The Twin Comanche calls for no flaps in take-off, because we don't want to take off while our airspeed is still below Vmc. In a nutshell, the aircraft will be uncontrollable below Vmc if an engine fails. So we want to stay above that at all times. Once we're cleared for take-off, and we've done our crew briefing and are ready to go, we push the power forward, and hold it on the runway centreline as we're sucked back into our seats. Right at about 80 mph, the airplane stops bouncing along the runway and starts flying. Now we'll accelerate in a level attitude just above the runway until we've past Vmc (90 mph) and reached our best rate of climb, which is 112 mph. At this point we'll pitch the nose up and climb out. As soon as we've run out of runway, which is about 5-10 seconds after our wheels left the ground, we transition into the normal climb. Landing gear goes up, we pull the power and props back to our climb setting, and we let our airspeed increase to around 130 to 140 mph for better cooling for the engines. Not long after, we've reached our cruising altitude, so its time for the cruise checklist. Power once again back to cruise power, electric fuel pumps can go off one at a time as we watch our fuel flow gauge for any decrease in fuel flow. If something is wrong with our engine driven fuel pumps we want to be able to identify which one, and if something is wrong with both of them it would also be really nice to not have both engines quit at the same time, cause that would just make for a bad day. The rest of the cruise checklist is pretty standard. Mixtures lean, fuel tank selectors as req'd (also done one at a time), cowl flaps closed, nav instruments set.
I'll post what we do for landing tommorrow maybe, because this is getting a little long and its also getting quite late, and I have to work tommorrow.
Just a heads up, this is going to be a fairly technical post, so those not interested in reading procedures and what-not, sorry. Otherwise read on!
For those of you out there who know what a Constant Speed Propeller is, feel free to skip these next two paragraphs, I just feel compelled to give a little background knowledge to those unaquainted with the complex aircraft.
First of all the term "Complex Aircraft" generally refers to an aircraft with retractable landing gear and a constant speed propeller, or in my airplane's case, propellers plural. A constant speed propeller is one where you can control the pitch of the blades. This gives you an advantage similiar to different gears in a car. A fine pitch in the propeller, similiar to a low gear, will give us lots of torque for the take-off and climb, whereas a coarse pitch, like a high gear, will give us a fast cruising speed.
In addition to a power control (controls amount of air aloud into engine) and mixture control (controls amount of fuel aloud into engine) we have a a set of Propeller controls. These don't directly control the pitch of the propeller blades, but actually control a governor that allows the blades to change their pitch in order to hold a constant engine RPM as directed by the prop controls. Hence the name "constant speed propeller". The governor, based on how much power is being delivered to the props by the engine, will adjust the pitch of the blades to either slow down, or speed up the engine as needed to maintain the set RPM. For example. Say we want to set our props to a cruise setting, and right now we have just finished our climb and are in a fine pitch climb setting of 2500 RPM. We will pull back the prop control levers until the Tachometer reads our desired RPM, which we will call 2300. The governor senses that right now the props are spinning at a faster rate then 2300, so it increases the pitch, which in turn loads the engine and slows it down to 2300. If we were to increase the power being delivered to the props by pushing our throttle forward, the props will naturally want to speed up, so the governor will once again increase the pitch of the props in an attempt to keep them spinning at 2300 RPM. So unlike a fixed pitch prop aircraft where power to the engine is measured on the Tachometer, we measure power from the Manifold Pressure Gauge, in Inches of Mercury, and we manage the prop settings using our Tachometer.
Now that we have a little background knowledge, I can talk about the procedures we use for taking off.
For taking off we use a full fine pitch setting for the props, full power to the engines, and no flaps. The Twin Comanche calls for no flaps in take-off, because we don't want to take off while our airspeed is still below Vmc. In a nutshell, the aircraft will be uncontrollable below Vmc if an engine fails. So we want to stay above that at all times. Once we're cleared for take-off, and we've done our crew briefing and are ready to go, we push the power forward, and hold it on the runway centreline as we're sucked back into our seats. Right at about 80 mph, the airplane stops bouncing along the runway and starts flying. Now we'll accelerate in a level attitude just above the runway until we've past Vmc (90 mph) and reached our best rate of climb, which is 112 mph. At this point we'll pitch the nose up and climb out. As soon as we've run out of runway, which is about 5-10 seconds after our wheels left the ground, we transition into the normal climb. Landing gear goes up, we pull the power and props back to our climb setting, and we let our airspeed increase to around 130 to 140 mph for better cooling for the engines. Not long after, we've reached our cruising altitude, so its time for the cruise checklist. Power once again back to cruise power, electric fuel pumps can go off one at a time as we watch our fuel flow gauge for any decrease in fuel flow. If something is wrong with our engine driven fuel pumps we want to be able to identify which one, and if something is wrong with both of them it would also be really nice to not have both engines quit at the same time, cause that would just make for a bad day. The rest of the cruise checklist is pretty standard. Mixtures lean, fuel tank selectors as req'd (also done one at a time), cowl flaps closed, nav instruments set.
I'll post what we do for landing tommorrow maybe, because this is getting a little long and its also getting quite late, and I have to work tommorrow.
First post, and a little about me
Ok so this is my first post in my new blog! I set up this blog as a means to write about my experiences in aviation and as some sort of a record of my aviation career (outside of the impersonal data recorded in my logbooks). It isn't really intended for a specific audience in particular, but I would imagine anyone who knows me personally, would enjoy it as well as anyone who is in aviation, or interested in it.
Well a little about me. I was born on June 17, 1985, so as of this writing I am 21. I am almost a commercial pilot, with just over 250 hours total time under my belt, with most of it being time in my own 1971 Cessna 150. I work full time as an AME Apprentice/Aircraft Groomer for a charter company out of London, Ontario.
Well I think that's enough about me, onto my first 'real' post!
Well a little about me. I was born on June 17, 1985, so as of this writing I am 21. I am almost a commercial pilot, with just over 250 hours total time under my belt, with most of it being time in my own 1971 Cessna 150. I work full time as an AME Apprentice/Aircraft Groomer for a charter company out of London, Ontario.
Well I think that's enough about me, onto my first 'real' post!
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