Mental dump of questions for PPL & CPL level

[mckenziepiping]

Answered

Is there a difference between Licensed Empty Weight (p. 16 of FTM) and Standard Empty Weight, which is a term I've seen thrown around in other references?

I am NOT referring to Basic Empty Weight.

[mckenziepiping]

Answered

The AIM provides this definition:

Daylight:
The period of time during any day that begins with the morning civil twilight and ends with the evening civil twilight.

Common sense tells me that daylight ends when civil twilight begins.... but the way this definition is worded could also mean that daylight INCLUDES civil twilight and that the end of daylight coincides with the end of evening civil twilight (since, after all, you can still "see" during evening civil twilight).....

So which is it? Does daylight end when evening twilight begins? Or does daylight end when evening twilight ends (at which point night has begun)?

[mckenziepiping]

Answered

Now, I know one should always take off with a headwind. However, I'm wondering about those situations where you might be forced to take-off with a quartering tailwind due to circumstances beyond your control.

In such a situation, would you start the take-off roll with the control column turned WITH the wind and apply forward pressure (as would be the case when taxiing with a quartering tailwind) and then gradually neutralize the elevator and turn the control column into wind as you build up enough speed to "cancel" the tailwind? Or would you just apply conventional crosswind takeoff inputs instead of complicating things as I've done above? Is there even a procedure for this or does it just boil down to PDM?

[mckenziepiping]

Answered

When learning the technique for "short-field landing over an obstacle", students are instructed to use a steeper glide path than usual (since you need to clear the obstacle).

I'm wondering about short-field landings WITHOUT an obstacle... is it still recommended to use a steeper glide path than you would for a normal approach?

[Mercator]

Now, I know one should always take off with a headwind. However, I'm wondering about those situations where you might be forced to take-off with a quartering tailwind due to circumstances beyond your control.

In such a situation, would you start the take-off roll with the control column turned WITH the wind and apply forward pressure (as would be the case when taxiing with a quartering tailwind) and then gradually neutralize the elevator and turn the control column into wind as you build up enough speed to "cancel" the tailwind? Or would you just apply conventional crosswind takeoff inputs instead of complicating things as I've done above? Is there even a procedure for this or does it just boil down to PDM?

Great question man!

1) Taking off with a tailwind is a very bad idea, keep in mind climb performance and obstacle clearance.

2) Forward pressure on take off roll will stress the nose gear, cause shimmy vibrations and damage- not a good idea.
Think of it as the elevators/ tail plane is down when the controls are moved forward and as power is added it makes the aircraft want to pitch down,adding more pressure and weight on the nose gear.

3) The effect of cross wind inputs on a quartering tailwind are advantageous only when the cross wind speeds exceed the slipstream produced by the propeller.

I am a believer of holding the control coloum aft under all taxiing light wind conditions to relieve the nose wheel oleo of any unnecessary forward pressure.

In a nutshell if a plan is made to take off in those conditions expect significant ground roll increase and significant decrease in climb performance.

An accident in Texas a few years ago, where a student pilot crashed in to a semi on the highway across the departure end of the runway when the pilot attempted to land and then overshoot in tail wind.
The aircraft couldnt climb a 100' mixed with high density altitude .

Overall on this a big NO NO, many student pilots read this forum and any reasoning on this question may impact there decision to attempt a take off in tail wind , no technique should be applied to take off in tail winds, especially in training piston aircrafts. I guess if there was any technique it would have been mentioned in the FTM or any other book.
If there is a situation beyond your control avoid being in control of a machine that flies on that day. )
With all due respect to your question.

[Posthumane]

In regards to your second question, about daylight, I understand that to mean that it is inclusive of the twilight periods.

“day” or “daylight” means the time between the beginning of morning civil twilight and the end of evening civil twilight

Morning civil twilight begins when the sun is 6 degrees below the horizon and ends with sunrise, and evening civil twilight begins at sunset and ends when the sun is 6 degrees below the horizon. It is also commonly thought of as the period when there is enough light to operate normally without additional light sources.

There are some specific regulations that say "from sunrise to sunset" or vice versa as opposed to daylight which explicitly exclude the twilight period, such as:

605.17 (1) Subject to subsection (2), no person shall operate an aircraft in the air or on the ground at night, or on water between sunset and sunrise, unless the aircraft position lights and anti-collision lights are turned on.

[photofly]

Check the details of that reg carefully: for aircraft in the air and on the ground the relevant lighting period is still "night". Sunrise and sunset is relevant only to aircraft on water which have to comply with the the watercraft regulations for lighting.

Different in the US iirc.


The two civil twilight periods are both "day" for aviation purposes.

[Posthumane]

Yes, that is what I was pointing out - lighting requirements for air and ground use "Night" (which is obviously the opposite of day as per the regs), whereas the water regulations use sunrise and sunset. The water lighting requirement includes night, and a small period of day (the twilight periods). Sorry if that wasn't clear.

Regarding the first question, Licensed Empty Weight is inclusive of optional equipment, so it's for a specific aircraft, but does not include full oil (only undrainable oil). Basic empty weight is the same thing but with full oil and unusable fuel. Standard empty weight is the basic empty weight minus optional equipment, so it is a weight that a manufacturer would specify for the basic aircraft before the customer adds in their chosen goodies. Licensed empty weight is not really used by manufacturers anymore.

[mckenziepiping]

In regards to your second question, about daylight, I understand that to mean that it is inclusive of the twilight periods.

“day” or “daylight” means the time between the beginning of morning civil twilight and the end of evening civil twilight

Morning civil twilight begins when the sun is 6 degrees below the horizon and ends with sunrise, and evening civil twilight begins at sunset and ends when the sun is 6 degrees below the horizon. It is also commonly thought of as the period when there is enough light to operate normally without additional light sources.

There are some specific regulations that say "from sunrise to sunset" or vice versa as opposed to daylight which explicitly exclude the twilight period, such as:

605.17 (1) Subject to subsection (2), no person shall operate an aircraft in the air or on the ground at night, or on water between sunset and sunrise, unless the aircraft position lights and anti-collision lights are turned on.

Thanks for clearing that up! I'm not yet at the stage where I can comfortably navigate the CARs and I'm still heavily reliant on the AIM, FTM and FTGU... and in this case, the AIM tried to simply the CARs but actually complicated them inadvertently LOL...

[mckenziepiping]

Now, I know one should always take off with a headwind. However, I'm wondering about those situations where you might be forced to take-off with a quartering tailwind due to circumstances beyond your control.

In such a situation, would you start the take-off roll with the control column turned WITH the wind and apply forward pressure (as would be the case when taxiing with a quartering tailwind) and then gradually neutralize the elevator and turn the control column into wind as you build up enough speed to "cancel" the tailwind? Or would you just apply conventional crosswind takeoff inputs instead of complicating things as I've done above? Is there even a procedure for this or does it just boil down to PDM?

Great question man!

1) Taking off with a tailwind is a very bad idea, keep in mind climb performance and obstacle clearance.

2) Forward pressure on take off roll will stress the nose gear, cause shimmy vibrations and damage- not a good idea.
Think of it as the elevators/ tail plane is down when the controls are moved forward and as power is added it makes the aircraft want to pitch down,adding more pressure and weight on the nose gear.

3) The effect of cross wind inputs on a quartering tailwind are advantageous only when the cross wind speeds exceed the slipstream produced by the propeller.

I am a believer of holding the control coloum aft under all taxiing light wind conditions to relieve the nose wheel oleo of any unnecessary forward pressure.

In a nutshell if a plan is made to take off in those conditions expect significant ground roll increase and significant decrease in climb performance.

An accident in Texas a few years ago, where a student pilot crashed in to a semi on the highway across the departure end of the runway when the pilot attempted to land and then overshoot in tail wind.
The aircraft couldnt climb a 100' mixed with high density altitude .

Overall on this a big NO NO, many student pilots read this forum and any reasoning on this question may impact there decision to attempt a take off in tail wind , no technique should be applied to take off in tail winds, especially in training piston aircrafts. I guess if there was any technique it would have been mentioned in the FTM or any other book.
If there is a situation beyond your control avoid being in control of a machine that flies on that day. )
With all due respect to your question.

Ah yes, I was not thinking about the slipstream... I was only thinking about the forward velocity of the aircraft vs the tailwind. But indeed, I guess we wouldn't need to worry about that tail wind picking up the tail since the full-throttle slipstream will blow it away... I get the other parts of your answer too but I'm only replying to this part because I was specifically wondering about the aerodynamics rather than the "best practices" aspect.

[photofly]

The ailerons are out of the prop wash; if you're being picky the ailerons should go "out of the wind" if the relative airflow is from behind the aircraft, for example when taxiing with a strong tailwind.

[mckenziepiping]

Answered

The first row in the table (C172S) attached to this post is confusing me. Notice how at higher altitudes, higher RPMs become acceptable and at 10 000ft you can redline the engine and it's considered "normal operation".

What is the reason for this? I suspect it relates to air density but I don't quite see how/why a prop spinning in thinner air (less resistance on the engine) is favourable...

[photofly]

It is not the case that higher RPMs become more acceptable; red line stays the same, as shown in the last column.

However 2700rpm at low altitude pumps enough air through the engine per minute that with a properly set mixture the power developed is greater than an acceptable continuous cruise power.

At high altitude even with the engine turning at red line the diminished air density means that insufficient oxygen is available per minute to burn fuel at a rate that will develop more power than the engine manufacturer recommends for continuous cruise. As far as RPM goes therefore you can fill your boots. Up to the redline of 2700RPM.

More RPM means more oxygen throughput per minute and therefore more fuel burned and more power developed. The disadvantage is that you get greater frictional and other losses in a faster turning engine. Tant pis.

Redline remains at 2700 at all altitudes.

[Mercator]

C172-S uses a normally aspirated engine.
True your question finds significance in relation with air density. However it's never ok to red line any engine as it causes engine damage.

In reference to the performance charts 60% power at 2000' was obtained at 2300 rpm standard day, but at 10000 you need 2500 rpm to produce the same effect.

In fact at 10000' a fully open throttle will probably produce in practical terms a max of 2550 rpm.
You would probably get 2700 rpm only at sea level, ISA conditions,mixture lean to peak rpm and on a brand new plane just out of the factory.

At 10k air is thinner the prop has to try hard to bite the air and the engine gets less air molecules in it to burn.
Overall the c172 kind of struggles at 10k.
It takes almost 30 mins to climb to 10000' in a 172 and the only reason I would do so in a 172 is if I find a 50 kt tailwind to ride in on a cross country.

On a cold day I took off and obtained 500 fpm corresponding to 80 kts ,after passing 7000' to get 500 fpm I had to pitch higher to indicate around 50-55 kts. If I remember 80 kts gave me around 100-150 fpm climb at full power.

In short performance reduces tremendously after passing 7000'.

The only way you can redline a c172 is on a descent, pitch down full power. DO NOT TRY IT, you may survive the flight but your flight school maintenance will be pretty pissed.

A little more detail into the power plant marking,indicates operation at 10000' and green arc maximum limit 2700 rpm, the chart does not indicate it's ok to redline the engine in any way.

The dangerous redline starts at 2700 and higher.

[mckenziepiping]

Thanks guys! I appreciate all the help. I have a huge list of questions I've amassed over my 80 hours of flying. I'm just starting to get back into the game after having been away for a year... there are WAY more questions to come; I just need to vet them first and make sure nothing is "stupid" since I know how quick people are to get at each other's throats on forums. It's great that I can clear up a lot of the confusion here because it'll be less of a burden on the staff at my flight school come next semester. Cheers!

[Mercator]

It's great that I can clear up a lot of the confusion here because it'll be less of a burden on the staff at my flight school come next semester. Cheers!

Hey man , no worries ! No such thing as a stupid question, my strong belief is that the people who ask stupid questions have the most intelligent solutions as well, so keep them going.

I am shocked but not surprised to see you considering yourself as a burden on your flight school, it's the moral responsibility of every flight school to answer your questions.

I see no reason for a flight school to consider your questions irrelevant,especially if you are signing your life away while funding them with the $60000 fee or more.
It's a dis-service if they take your money and rake in hours under there belt. Get your instructors to find you the answers to tough questions as you pay them a fee for it ! Right!

There are cases where students don't care and are in it only for the beer.....good luck to them, your questions are genuinely thought provoking.
It's not the stupid questions, it's the stupid instructors I fear! Report your instructor if he can't get your answers or doesn't care!

[mckenziepiping]

It's great that I can clear up a lot of the confusion here because it'll be less of a burden on the staff at my flight school come next semester. Cheers!

Hey man , no worries ! No such thing as a stupid question, my strong belief is that the people who ask stupid questions have the most intelligent solutions as well, so keep them going.

I am shocked but not surprised to see you considering yourself as a burden on your flight school, it's the moral responsibility of every flight school to answer your questions.

I see no reason for a flight school to consider your questions irrelevant,especially if you are signing your life away while funding them with the $60000 fee or more.
It's a dis-service if they take your money and rake in hours under there belt. Get your instructors to find you the answers to tough questions as you pay them a fee for it ! Right!

There are cases where students don't care and are in it only for the beer.....good luck to them, your questions are genuinely thought provoking.
It's not the stupid questions, it's the stupid instructors I fear! Report your instructor if he can't get your answers or doesn't care!

Perhaps my choice of words painted my school in an unfairly negative light. There are plenty of staff members there who enjoy going through my questions with me, since I tend to find loopholes/pleonasms/ambiguity in things and extremize every statement to verify the outcome. I also take things overly literally, which, in aviation, is undesirable since people need to "just get it" instead of requiring a 100% precise explanation for everything. I don't know how many contradictory definitions I've read regarding the words "lift" and "induced drag" (FTGU being one of the worst culprits). Anyway, I digress. The truth is that I hold a PPL and so far everything I've asked pertains to pre-PPL knowledge, so I'd rather minimize the questions where I "ought to know" the answer so that I don't draw attention to myself as someone who "regressed in skill level" after an absence of 14 months.

[mckenziepiping]

Not answered

The attachment is from the RIC-21: Study Guide for the Restricted Operator Certificate.

In this situation, when they say "all transmissions shall cease", are they referring only to the frequency in use by the aircraft in distress? Or are they banning all transmissions on ALL frequencies within the geographic area where the situation is occurring? Could other aircraft in the area switch to a different frequency in order to coordinate their actions....?

[mckenziepiping]

Answered

Also from the same document (see attachment).... the statement about "April 1st of each year"..... am I supposed to be paying an annual renewal for my ROC? I move around a lot so I can never count on receiving a bill in the mail....

[photofly]

ROC-A is not a radio station licence. (It's neither a licence not is it for a station.) There are no renewal fees.

[mckenziepiping]

It is not the case that higher RPMs become more acceptable; red line stays the same, as shown in the last column.

Yes but the 2700rpm appears both in the last column and in the "normal operation" column, which would suggest that, at 10 000ft, having a red-lined engine at 2700rpm is considered normal operation, no?

However 2700rpm at low altitude pumps enough air through the engine per minute that with a properly set mixture the power developed is greater than an acceptable continuous cruise power.

I guess what I'm not getting is why it's inherently "bad" to develop too much power. I get that it's bad for rpm's to be too high since each part in the engine has a design rotational speed... but whether you're at 2700rpm at low altitude or 2700rpm at high altitude, the engine is still rotating at 2700rpm and so the stresses on all the mechanical parts seem to be the same. You're saying that 2700rpm at high altitude would develop the "right" amount of power, given the oxygen-poor environment, but at low altitude, it would develop "too much" power, due to the surplus of oxygen... what I don't get is why it's fine to red line the engine as long as it's not producing too much power but it's not fine to redline it when it is producing too much power.

[mckenziepiping]

In reference to the performance charts 60% power at 2000' was obtained at 2300 rpm standard day, but at 10000 you need 2500 rpm to produce the same effect.

Ok so then it's not the RPM that determines whether or not the engine may get damaged - it's the %power?

In fact at 10000' a fully open throttle will probably produce in practical terms a max of 2550 rpm.

So is it meaningless for the "normal operation" column to indicate 2100 - 2700 at 10 000ft since you wouldn't be able to achieve that RPM anyway? A publishing oversight, perhaps?

A little more detail into the power plant marking,indicates operation at 10000' and green arc maximum limit 2700 rpm, the chart does not indicate it's ok to redline the engine in any way.

Ok so the fact that the range 2100 - 2700 is in the "normal operation" column does not mean that every setting within that range is "ok"? I would have thought "normal operation" means "use any settings prescribed here and it's safe".

[mckenziepiping]

ROC-A is not a radio station licence. (It's neither a licence not is it for a station.) There are no renewal fees.

Oh I see... so in this context when they say "license" they are not referring to something that is held by an individual person... they are referring to a license that allows the station to be operated by SOMEONE, regardless of who that someone is.....

[mckenziepiping]

Answered

Does anyone know where the aileron type and flap type for a 172 would be published? The POH for the 172S does not contain this information.

The 172S I train on has frise differential ailerons and single-slotted fowler flaps. I know this from word-of-mouth and observing the airframe of the aircraft for myself. However, since this kind of question comes up on flight tests, I would like to know where I can see it published.

This guy on another forum is wondering about the same thing: http://www.airliners.net/aviation-forum ... ain/70299/

[photofly]

I guess what I'm not getting is why it's inherently "bad" to develop too much power. I get that it's bad for rpm's to be too high since each part in the engine has a design rotational speed... but whether you're at 2700rpm at low altitude or 2700rpm at high altitude, the engine is still rotating at 2700rpm and so the stresses on all the mechanical parts seem to be the same. You're saying that 2700rpm at high altitude would develop the "right" amount of power, given the oxygen-poor environment, but at low altitude, it would develop "too much" power, due to the surplus of oxygen... what I don't get is why it's fine to red line the engine as long as it's not producing too much power but it's not fine to redline it when it is producing too much power.

Too much power is too much heat.

Too many RPM is too much mechanical stress on the engine parts.

Neither is good. The RPM is a hard limit. The engine is not to be run above 2700RPM, for any amount of time now matter how short. End of story.

You may run at up to and including 100% of rated power (that's why it's the rated power) but not for extended periods of time. For the cruise portion of flight Cessna sets upper limits on RPM to limit the level of continuous power. The power developed at a given RPM depends on altitude and air temperature, though. Here's an example:

According to the 172S cruise performance table the following are acceptable for continuous cruise:

At 8000' and 20 below standard temperature (therefore at -21°C OAT) 2700RPM is approved for use and develops 83% of rated BHP.

At 2000' and 20 below standard temperature (-9°C) 2550RPM also develops 83% BHP. They don't approve more than 2550RPM at that altitude.

At no altitude is more than 2700RPM approved. Whether there is a throttle setting for which the engine will turn that fast in level flight is a red herring: you can always overspeed the engine in a dive, at any altitude. Don't.