Stuck!
Thread Starter
Join Date: Nov 2007
Location: UK
Age: 38
Posts: 75
Likes: 0
Received 0 Likes
on
0 Posts
Stuck!
Stuck on a question on my flight planning... can someone explain how this graph works given the information etc?
Hope this is the right place to post this....
ImageShack - Image Hosting :: helpsu9.jpg
Hope this is the right place to post this....
ImageShack - Image Hosting :: helpsu9.jpg
Join Date: Feb 2007
Location: Amsterdam
Posts: 4,598
Likes: 0
Received 0 Likes
on
0 Posts
Yep. Seems like a duff question.
CofG is 42 inches aft of datum which is way off the chart and my experience tells me that with a graph like that, even with a very unusual loading you cannot even get the CofG that far forward - unless you fill the back with helium balloons or something.
(Oh, and for your conscience: yes, this is the right place to post questions like this. Even better now that I won a Sharp LCD TV...
)
CofG is 42 inches aft of datum which is way off the chart and my experience tells me that with a graph like that, even with a very unusual loading you cannot even get the CofG that far forward - unless you fill the back with helium balloons or something.
(Oh, and for your conscience: yes, this is the right place to post questions like this. Even better now that I won a Sharp LCD TV...
)
Moderator
Hi Dave,
The image does not seem to come across legibly, but in general:
The weight and balance "envelope" as depicted is showing you the maximum permissible center of gravity limits relative, and up to, the maximum gross weight. The actual aircraft weight for the proposed flight, once known by calculation, is plotted up the left side of the graph. Using the calculated C of G (from loading charts provided elsewhere for you, you will have calculated the total aircraft C of G position (doing so may require calculating the moment too, and working backward a bit). You then locate the C of G position along the weight line which you have identified on the chart.
If the plotted C of G position lies outside (left or right) the "envelope" entirely, flight is not permitted. (if it's too high, you're too heavy!) If the plotted point lies inside the "normal" envelope, you may fly the aircraft as a normal category aircraft, and only perform the manuevers stated in the limitations for that type of flight. If the plotted point lies within the "utility" portion of the envelope, additional manuevers (probably including spins) will be permitted. This is to be taken to mean that spins would not be permitted if the C of G point is in the normal envelope. Generally, if it is in the "utility" you may also fly as a "normal" category, though you might be having seat occupancy limitations.
Refer to the actual flight manual (if applicable) for the real information, as what I have told you is only the concept.
If that does not answer the question, let us know in greater detail what you need to know.
Pilot DAR
The image does not seem to come across legibly, but in general:
The weight and balance "envelope" as depicted is showing you the maximum permissible center of gravity limits relative, and up to, the maximum gross weight. The actual aircraft weight for the proposed flight, once known by calculation, is plotted up the left side of the graph. Using the calculated C of G (from loading charts provided elsewhere for you, you will have calculated the total aircraft C of G position (doing so may require calculating the moment too, and working backward a bit). You then locate the C of G position along the weight line which you have identified on the chart.
If the plotted C of G position lies outside (left or right) the "envelope" entirely, flight is not permitted. (if it's too high, you're too heavy!) If the plotted point lies inside the "normal" envelope, you may fly the aircraft as a normal category aircraft, and only perform the manuevers stated in the limitations for that type of flight. If the plotted point lies within the "utility" portion of the envelope, additional manuevers (probably including spins) will be permitted. This is to be taken to mean that spins would not be permitted if the C of G point is in the normal envelope. Generally, if it is in the "utility" you may also fly as a "normal" category, though you might be having seat occupancy limitations.
Refer to the actual flight manual (if applicable) for the real information, as what I have told you is only the concept.
If that does not answer the question, let us know in greater detail what you need to know.
Pilot DAR
Thread Starter
Join Date: Nov 2007
Location: UK
Age: 38
Posts: 75
Likes: 0
Received 0 Likes
on
0 Posts
This is exactly what i thought...... total mass of the plane divided by the total moment should give you the moment of the datum, but 42 shows nowhere on the graph... that's why I was confused... thought I was doing something wrong, couldn't even find it in my PPL manuals.. 
Thread Starter
Join Date: Nov 2007
Location: UK
Age: 38
Posts: 75
Likes: 0
Received 0 Likes
on
0 Posts
Join Date: Sep 2005
Location: Norfolk UK
Age: 80
Posts: 1,200
Likes: 0
Received 0 Likes
on
0 Posts
Dave,I tried the demo and it seems a good site although I found an error with another unrelated question but can't remember what it was now
I used www.airquiz when I was a student and found it to be very useful.
Good luck
Lister
I used www.airquiz when I was a student and found it to be very useful.
Good luck
Lister
Thread Starter
Join Date: Nov 2007
Location: UK
Age: 38
Posts: 75
Likes: 0
Received 0 Likes
on
0 Posts
ImageShack - Image Hosting :: helpja1.jpg
Can anyone tell me the calculations to working this question out?
Can anyone tell me the calculations to working this question out?
Thread Starter
Join Date: Nov 2007
Location: UK
Age: 38
Posts: 75
Likes: 0
Received 0 Likes
on
0 Posts
Edit... PPLQuiz giving me wrong answers again. Im presuming the last caluclation of an addition is correct?
PPLQUIZ said 338 was the right answer
PPLQUIZ said 338 was the right answer
Last edited by DaveD; 16th Feb 2009 at 10:12.
Join Date: Sep 2003
Location: UK,Twighlight Zone
Posts: 0
Likes: 0
Received 0 Likes
on
0 Posts
What is pressure altitude Dave?
If you were on the ground you would find your pressure altitude by setting 1013 on the altimeter subscale. So you need to add any difference between your current setting and 1013 if lower or deduct it if higher.
Pressure altitude is the height in the standard atmosphere above the 1013.2mb (hpa) pressure level at which the pressure equals that of the aircraft or point under consideration.
Join Date: Jan 2006
Location: An island somewhere
Posts: 423
Likes: 0
Received 0 Likes
on
0 Posts
Well, bose-x's calculation is wrong ... as are all of the possible answers given!
Pressure altitude is what the altimeter reads if 1013mb is set on the sub-scale.
If the altimeter reads zero when 992mb is set, it will read 630ft with 1013mb set.
The airfield elevation is a distractor in this question. Unfortunately, it also distracted the questioner!
Pressure altitude is what the altimeter reads if 1013mb is set on the sub-scale.
If the altimeter reads zero when 992mb is set, it will read 630ft with 1013mb set.
The airfield elevation is a distractor in this question. Unfortunately, it also distracted the questioner!