Why don't people know the difference between True Airspeed, and Indicated Airspeed...RANT

FastEddieB said:
Careful!

You might be “probing”.
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It's one thing to start off with a misleading question. It is another thing entirely to follow a student's statement with a question.
 
Tarheelpilot said:
In that case I’m not sure where to start.

Knowing density altitude is essential for flight planning purposes at high altitude airports and can also be a factor at lower altitude airports if they are short enough. To me when you say that knowing the density altitude is not important would be the same attitude and poor decision making as someone saying it’s not important to know how much gas is onboard. You should rethink your attitude regarding DA and perhaps spend some time talking to a pilot that can show you how much benefit can be gained in your airmanship skills by incorporating it in your flying. If you only fly sea level airports in a plane that’s always well below gross from long runways suitable for jets then perhaps you can get away with not understand and using DA info. In other circumstances it’s critical information.
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I think what he is getting at is, it doesn’t matter if you know your actual DA just as long as you have consulted your POH for those conditions. I’d agree in that it doesn’t matter what the actual DA number is, all I need to know is if my airplane / helicopter can get in and out of there.
 
Velocity173 said:
I think what he is getting at is, it doesn’t matter if you know your actual DA just as long as you have consulted your POH for those conditions. I’d agree in that it doesn’t matter what the actual DA number is, all I need to know is if my airplane / helicopter can get in and out of there.
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The POH data stops at 8,000 ft. The ground elevation is 7,500 ft and the OAT is 25 degrees C. Whatchagonnado? Big Bear it into the hillside?
 
Clark1961 said:
The POH data stops at 8,000 ft. The ground elevation is 7,500 ft and the OAT is 25 degrees C. Whatchagonnado? Big Bear it into the hillside?
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My AA5 POH only goes to 6000 ft but I meant “POH” as a generic term anyway. Plenty of other manuals cover all the way to max altitude. If it’s not covered than obviously do your best on an extended scale. Unless the DA will be an aircraft limitations factor or, it must be calculated for a flight manual that doesn’t already do the calculation, the actual number isn’t important.
 
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Tarheelpilot said:
In that case I’m not sure where to start.
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If I were you, I'd start by actually reading the question rather than making faulty assumptions about what I do or do not think is important.

Knowing density altitude is essential for flight planning purposes at high altitude airports and can also be a factor at lower altitude airports if they are short enough. To me when you say that knowing the density altitude is not important would be the same attitude and poor decision making as someone saying it’s not important to know how much gas is onboard. You should rethink your attitude regarding DA and perhaps spend some time talking to a pilot that can show you how much benefit can be gained in your airmanship skills by incorporating it in your flying.
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So far, @denverpilot is the only one who's actually come up with an answer. Clearly, since you don't understand the question, you won't have an answer.
If you only fly sea level airports in a plane that’s always well below gross from long runways suitable for jets then perhaps you can get away with not understand and using DA info. In other circumstances it’s critical information.
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I don't only fly from sea level airports. I've operated fairly regularly from airports with density altitudes well above 10,000 feet. Yes, many of them were long enough for jets...just barely. But as I indicated in previous posts, knowing the density altitude didn't matter in my performance calculations. Either the airplane's charts used pressure altitude and temperature, and therefore didn't need an intermediate density altitude calculation, or it didn't have any performance data at all, in which case I used a method that's more complete and accurate than most light plane charts are to start with.

So...back to the question. If you have charts, why does a density altitude matter; if you don't have charts, how do you use density altitude to determine your takeoff distance, landing distance, or climb rate?
 
Clark1961 said:
The POH data stops at 8,000 ft. The ground elevation is 7,500 ft and the OAT is 25 degrees C. Whatchagonnado? Big Bear it into the hillside?
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That's my question. You seem to be claiming it's important to know what the DA is. How do you use it to determine takeoff/landing distances or climb performance?
 
MauleSkinner said:
That's my question. You seem to be claiming it's important to know what the DA is. How do you use it to determine takeoff/landing distances or climb performance?
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How are you going to know those things without some sort of reference?
 
MauleSkinner said:
If I were you, I'd start by actually reading the question rather than making faulty assumptions about what I do or do not think is important.


So far, @denverpilot is the only one who's actually come up with an answer. Clearly, since you don't understand the question, you won't have an answer.

I don't only fly from sea level airports. I've operated fairly regularly from airports with density altitudes well above 10,000 feet. Yes, many of them were long enough for jets...just barely. But as I indicated in previous posts, knowing the density altitude didn't matter in my performance calculations. Either the airplane's charts used pressure altitude and temperature, and therefore didn't need an intermediate density altitude calculation, or it didn't have any performance data at all, in which case I used a method that's more complete and accurate than most light plane charts are to start with.

So...back to the question. If you have charts, why does a density altitude matter; if you don't have charts, how do you use density altitude to determine your takeoff distance, landing distance, or climb rate?
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I didn’t make assumptions. You didn’t clearly communicate what your point was in my opinion. Frankly I think it comes down to one of the pit falls of communicating on a form.

Since you have experience at high altitude airports I don’t know why you are asking the question. You already know. Charts work off of temperature and pressure altitude which is what DA is. If you’re outside of the scope of your charts then knowing your da can help predict the performance of your aircraft based off of data you do have. If you’re operating an aircraft without any data and you pay attention to DA then over time you can get some benchmarks for expected performance. So just what are you asking??? It sounds like you already know the answer to your question.
 
Tarheelpilot said:
I didn’t make assumptions. You didn’t clearly communicate what your point was in my opinion. Frankly I think it comes down to one of the pit falls of communicating on a form.

Since you have experience at high altitude airports I don’t know why you are asking the question. You already know. Charts work off of temperature and pressure altitude which is what DA is. If you’re outside of the scope of your charts then knowing your da can help predict the performance of your aircraft based off of data you do have. If you’re operating an aircraft without any data and you pay attention to DA then over time you can get some benchmarks for expected performance. So just what are you asking??? It sounds like you already know the answer to your question.
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Experience is great...but how do you determine your performance knowing density altitude if you've never taken off that that DA before? What's the conversion factor from a known takeoff distance at a 7000 foot DA to a 10,000 foot DA? People are saying it's important to know the DA...but nobody seems to know how to use it to determine performance.

As I said, I don't...I use other methods. Yes, PA and temperature combine to make DA, but almost none of the methods I've seen actually determine or use DA.

If you have a method that works, I'd love to hear it.
 
MauleSkinner said:
Experience is great...but how do you determine your performance knowing density altitude if you've never taken off that that DA before? What's the conversion factor from a known takeoff distance at a 7000 foot DA to a 10,000 foot DA? People are saying it's important to know the DA...but nobody seems to know how to use it to determine performance.

As I said, I don't...I use other methods. Yes, PA and temperature combine to make DA, but almost none of the methods I've seen actually determine or use DA.

If you have a method that works, I'd love to hear it.
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Disagree... when you use the takeoff performance charts, whether you realize it or not, through the backdoor you are actually calculating DA... and how your aircraft will perform. I think that’s what is meant by “calculate density Altitude”.

I also believe you’re plenty smart enough to realize what I just said.
 
Kritchlow said:
Disagree... when you use the takeoff performance charts, whether you realize it or not, through the backdoor you are actually calculating DA... and how your aircraft will perform. I think that’s what is meant by “calculate density Altitude”.

I also believe you’re plenty smart enough to realize what I just said.
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I realize what you just said...I just don't see that as what people are saying when they say knowing the DA helps. Nor does it answer my question about how knowing DA gives you any kind of accurate performance information when charts for your airplane don't exist or go high enough, which is another assertion that has been made.
 
MauleSkinner said:
I realize what you just said...I just don't see that as what people are saying when they say knowing the DA helps. Nor does it answer my question about how knowing DA gives you any kind of accurate performance information when charts for your airplane don't exist or go high enough, which is another assertion that has been made.
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But to some point I think we are playing semantics here...
 
MauleSkinner said:
Ok. So you have the reference. What do you do with it? You don't seem to have any answer to that question either.
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I think it is more of you don't like my answer. If you have experience then you can relate performance to the calculated DA. If you don't have experience you can use it to extrapolate outside the performance tables. Or you can just say there is no point. It really doesn't matter to me at this point when you deny it so vehemently.

On the other hand there is the case of the otherwise fine pilot who departed BJC with a density altitude of what? prolly around 8,000 ft in a PA-28-235. Did he really think about having enough ceiling to clear a pass that was 7,000 higher ground elevation? Prolly not. He likely never had a chance. Maybe that DA thing is important.
 
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bflynn said:
I was a sailor long before I was an aviator. There are very few landmarks on the ocean, I get dead reckoning. How do you accomplish it on the sea? You sail so your track is going in the direction you want. But no matter how good your boat is, you're going to get downwind drift, so your heading isn't the same as your course heading. You're always crabbing at least a little in sailing. Unless there's no wind and then you're not sailing, you're drifting.
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Apparently the FAA has a different definition for dead reckoning, as referenced by publication FAA-H-8083-25B, Pilot's Handbook of Aeronautical Knowledge, page 16-13 (see attached). My original question was "When flying by dead reckoning..." so that sort of implies the FAA definition.

2d2deuc.png
 
MauleSkinner said:
Experience is great...but how do you determine your performance knowing density altitude if you've never taken off that that DA before? What's the conversion factor from a known takeoff distance at a 7000 foot DA to a 10,000 foot DA? People are saying it's important to know the DA...but nobody seems to know how to use it to determine performance.

As I said, I don't...I use other methods. Yes, PA and temperature combine to make DA, but almost none of the methods I've seen actually determine or use DA.

If you have a method that works, I'd love to hear it.
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Since you already have a method that works how about sharing that instead of asking patronizing questions that make me think Tom d stole your login credentials.
 
asicer said:
Apparently the FAA has a different definition for dead reckoning, as referenced by publication FAA-H-8083-25B, Pilot's Handbook of Aeronautical Knowledge, page 16-13 (see attached). My original question was "When flying by dead reckoning..." so that sort of implies the FAA definition.

2d2deuc.png
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Okay... but to be honest at low level GA altitudes TAS isn’t that far off from indicated.

I know we’re not talking airliners here, but that changes DRASTICALLY at high altitude and high airspeeds.
 
Kritchlow said:
But to some point I think we are playing semantics here...
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To some point...but to a greater extent, I think people are just spouting the FAA party line that knowing density altitude is important without any clue what to do with it. For example:
Clark1961 said:
If you have experience then you can relate performance to the calculated DA. If you don't have experience you can use it to extrapolate outside the performance tables.
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But after repeated requests, no information about how to extrapolate the data. Apparently he's just trying to impress us with his vocabulary.
 
MauleSkinner said:
To some point...but to a greater extent, I think people are just spouting the FAA party line that knowing density altitude is important without any clue what to do with it. For example:

But after repeated requests, no information about how to extrapolate the data. Apparently he's just trying to impress us with his vocabulary.
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If you don't know how to extrapolate then I can't help you. Welcome to graduate school.
 
Clark1961 said:
LOL, didn't say that I can't explain. I said that I can't help you.
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I'm not asking you to help me...I'm asking you to explain it for all those poor misguided, brainwashed souls who think DA is a useful calculation.

But apparently you don't give a rat's ass about anybody's life beyond pointing out how they died because they're not as smart as you.
 
MauleSkinner said:
I'm not asking you to help me...I'm asking you to explain it for all those poor misguided, brainwashed souls who think DA is a useful calculation.

But apparently you don't give a rat's ass about anybody's life beyond pointing out how they died because they're not as smart as you.
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LOL. Nice try but your closed mind doesn't cover anybody but you. If you really want training in high DA airport operations I will offer you a course. The tuition will be $20,000 because I think you will be a really poor student. Anything else?
 
Clark1961 said:
I'm of the mindset that probing is not teaching. Probing immediately sets up potential for conflict which is a negative environment for learning.
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Yup. Case in point? Our very own Tom D. When he starts with the probing questions, I'm like meh, whatever, and change the channel.
 
I've got no skin in this game, but that is also the definition of dead reckoning in a boat as well. Spend time on the Maine coast in the fog before GPS.. that's the only way to get around
asicer said:
Apparently the FAA has a different definition for dead reckoning, as referenced by publication FAA-H-8083-25B, Pilot's Handbook of Aeronautical Knowledge, page 16-13 (see attached). My original question was "When flying by dead reckoning..." so that sort of implies the FAA definition.

2d2deuc.png
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asicer said:
Apparently the FAA has a different definition for dead reckoning
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I guess you don't realize that you just agreed with me. Relax, you're making this into something it isn't and I don't understand why.
 
MauleSkinner said:
Just don't ask questions...apparently that makes you closed-minded.
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When you repeat the same question several times without engaging on the responses then you are deemed closed-minded. You decided the answer before you asked the question and refused alternative points of view.
 
MauleSkinner said:
I'm not asking you to help me...I'm asking you to explain it for all those poor misguided, brainwashed souls who think DA is a useful calculation.

But apparently you don't give a rat's ass about anybody's life beyond pointing out how they died because they're not as smart as you.
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I have a Long EZE owners manual that requires the pilot to compute DA to get landing / take off distances. I have a B407 flight manual that requires the pilot to compute DA in order to determine tail rotor effectiveness vs X-wind component at altitude.

So, there are times when pilots need to know actual DA in order to be within performance or limitation parameters.
 
bflynn said:
I guess you don't realize that you just agreed with me. Relax, you're making this into something it isn't and I don't understand why.
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Sorry, I misread your answer (I blame the tiny phone screen :)).

So if I understand things correctly, your answer to my question:
"When flying by dead reckoning, how do you calculate a crosswind correction?"

Is (paraphrased):
"I don't fly by dead reckoning because it's as useless as TAS"
 
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