Jump to content

Left tank dry, right tank 12 gallons left


Stacy

Recommended Posts

Agreed, conditions have to be right to test.  A steady track crosswind would be best to test.

 

BTW, I get confused by your apparent use of "shear" to mean "wind"...

 

A steady state wind will produce no results.  In a steady state crosswind once your heading or track is acquired there will be no need for correcting turns and without correcting turns you cannot try to establish if the AP is providing correction in response to loosing its heading or its course.  The only way your test can succeed is if corrections due to shear are needed.

 

Its possible you might need corrections because you plane doesn't fly strait and that's a third reason corrections could happen.  Hand flying while maintaining heading should tell you if your plane flies strait or if it needs turns to correct for rigging.  I think such turns probably always need to be to the same direction, left or right.

 

I never use shear to mean wind.  Shear is a change in wind either velocity or direction.  I think most pilots think of it as a change that results in an increase or a decrease in airspeed. Certainly negative shear on approach is a concern you may or may not recognize it and react. You may or may not have sufficient power available to remain above stall. 

 

Shear occurs when winds collide, turbulence is shear and can be mechanical or convective.  When you encounter a downdraft or an updraft you have a change in winds that causes a change in the relative wind and that's shear.

 

Back to the AP, winds don't blow your of course or off heading but shear does.

 

Edit:  In a steady state wind no control input is needed.  As soon as shear is experienced your speed/track/altitude is disturbed and throttle/control input is often needed to re-establish your speed track and altitude.

 

Same for the AP in steady state crosswind it has nothing to do but monitor and when shear is encountered correcting turns and or climbs or descents need control input to initiate.  

 

Wind = do nothing; Shear = fly the plane :) 

Link to comment
Share on other sites

  • Replies 58
  • Created
  • Last Reply

A steady state wind will produce no results.  In a steady state crosswind once your heading or track is acquired there will be no need for correcting turns and without correcting turns you cannot try to establish if the AP is providing correction in response to loosing its heading or its course.  The only way your test can succeed is if corrections due to shear are needed.

 

Its possible you might need corrections because you plane doesn't fly strait and that's a third reason corrections could happen.  Hand flying while maintaining heading should tell you if your plane flies strait or if it needs turns to correct for rigging.  I think such turns probably always need to be to the same direction, left or right.

 

I never use shear to mean wind.  Shear is a change in wind either velocity or direction.  I think most pilots think of it as a change that results in an increase or a decrease in airspeed. Certainly negative shear on approach is a concern you may or may not recognize it and react. You may or may not have sufficient power available to remain above stall. 

 

Shear occurs when winds collide, turbulence is shear and can be mechanical or convective.  When you encounter a downdraft or an updraft you have a change in winds that causes a change in the relative wind and that's shear.

 

Back to the AP, winds don't blow your of course or off heading but shear does.

 

 

Winds don't blow you off a heading, but they sure as hell blow you off a course line!  A course is a line from point A to Point B.  A heading is simply "point my nose at this number on the compass (or GPS, or whatever heading device) and fly".  If you have a course and are using an autopilot, the AP will correct for the wind to keep you on the course line between the starting point, and the direction the course was set to when you activated the AP.

 

If you are flying a heading, the AP is NOT correcting for the wind, and it will let you fly essentially wherever the wind takes you, while keeping your nose pointed at the set number on the heading instrument. When ATC asks you to fly a heading, this is what they are asking for.  

 

All you have to do to see if your AP is flying a course or a heading is to start the AP from a known point on the ground to another known point on the ground in a known direction, preferably where there is a crosswind.  If your ground track takes you in a straight line to the destination, you're flying a course.  If the ground track is curved, you are flying a heading (and will probably never actually reach your destination in any significant wind).

 

Giving an AP a course is essentially the same as giving it a GPS nav point.  It's a spot on the map to draw a straight line to; the AP will stay on that line.  The only difference in the CRS mode is that the destination point is a spot on the heading device corresponding to the CRS selected, that continually moves out to the horizon so there is never an "arrival".  This is not what ATC is asking for most times, so it's important to know how the AP behaves.  Since I don't know (yet) which mine does, when asked to fly a heading I step down the automation and hand fly the heading given. 

Link to comment
Share on other sites

Charlie Tango, I have figured out what you mean by shear, but I believe you are misusing the term.  Shear is wind moving in different directions meeting at some point in space.  If you are encountering a wind at 0° at 10kt and encounter a sudden wind change to 90° at 10kt, that is a shear event.  But if you have wind at 0° at 10kt and encounter a sudden 30kt wind, also from 0°, that is not shear, that is a gust.

 

The way you are using the term, it sounds like you mean shear to be any change in wind speed requiring correction regardless of direction.  That is an incorrect use of the term.  IMO of course, I'm sure if I'm wrong on this I'll get beaten up presently.   :D

Link to comment
Share on other sites

Winds don't blow you off a heading, but they sure as hell blow you off a course line!  A course is a line from point A to Point B.  A heading is simply "point my nose at this number on the compass (or GPS, or whatever heading device) and fly".  If you have a course and are using an autopilot, the AP will correct for the wind to keep you on the course line between the starting point, and the direction the course was set to when you activated the AP....

 

 

I understand what you mean in the first sentence: Winds don't blow you off a heading, but they sure as hell blow you off a course line! 

 

You are 100% wrong on that.  We have established that wind is steady state if its not its shear.

 

One of the two wind or shear can disturb you and require correcting turn(s).  That one is shear, wind (remember steady state) cannot disturb the aircraft and cause it to loose either course or heading.

 

You are trying to differentiate between being disturbed and loosing course but not heading.  These two are not the same but it takes shear to cause either one and wind alone cannot cause either.

 

The key concept to get this is that the plane doesn't 'know' that it is flying in wind.  The relative wind on the nose is the same with or without wind. Think of a hot air balloon that flies at zero air-speed it only drifts with the air-mass.  When you are a passenger there is no sense of wind it is dead calm, that is of course unless you encounter shear.

 

Your CT is like the hot air balloon in that it too drifts with the air-mass and negates any effect (except ground speed and track) of the wind on your CT.

 

Your wrong here too: If you have a course and are using an autopilot, the AP will correct for the wind to keep you on the course line between the starting point, and the direction the course was set to when you activated the AP....

 

You are blaming wind for what happens when you encounter shear.  The wind has no effect on your track or heading because your AP establishes its course/heading with a correcting crab angle.  You drift with the current air mass until it changes (shear) and only then do you need correcting turn(s).

Link to comment
Share on other sites

Charlie Tango, I have figured out what you mean by shear, but I believe you are misusing the term.  Shear is wind moving in different directions meeting at some point in space.  If you are encountering a wind at 0° at 10kt and encounter a sudden wind change to 90° at 10kt, that is a shear event.  But if you have wind at 0° at 10kt and encounter a sudden 30kt wind, also from 0°, that is not shear, that is a gust.

 

The way you are using the term, it sounds like you mean shear to be any change in wind speed requiring correction regardless of direction.  That is an incorrect use of the term.  IMO of course...

 

You can try to argue that gusts are not shear if you want, lots of people try to find a distinction (none exists).  If you were right that a gust is not shear well then what is it?  It sure isn't steady state wind.  If you cannot differentiate between steady state wind and shear there isn't a good enough basis for a conversation on this subject.

 

Look at your definition of shear in the quote.  You describe one kind of shear but there are many others and they are all common.  At our airport environment shear is a big problem that is a factor in most of the mishaps here.  Its the result of south winds colliding with east/west ridges resulting in eddies that collide again with ridges.  Its all mechanical turbulence resulting in shear that a CT can't land in.  Downdrafts are a big concern, classic shear where  if you remain level you loose your airspeed.  

 

Closing:  If we can't discuss wind as steady state and gusts/turbulence/shear as wind that is not steady state then the fundamentally / primarily important concept of steady state wind ceases to exist and wind the means everything but calm.  If winds mean almost everything but calm your claims become true.

Link to comment
Share on other sites

Three of the most common things winds do are undulate, rise and sink, and accelerate.  These are all wind shear but they are not all the same.

 

California is easy to understand, the mountains are big and run north and south.  An of course prevailing winds cross these mountains of at a 90* angle.  As winds cross mountains in this fashion and undulation sets up causing a series of waves that are sometimes visible in the form of lenticular clouds.  The Pacific gives us stead state / laminar flow west winds and California's terrain turns them into a series of waves (lots of wind shear).

 

Winds are influenced by mountain passes. You end up with a venturi effect at the pass and the wind accelerates as it approaches and departs.  Acceleration is shear.

 

Convective activity is common and both rising and sinking air represent shear too.

Link to comment
Share on other sites

Stacy,

I'm sorry this thread got hijacked. Here are my thoughts:

  1. Clear fuel sight gauges are absolutely critical in a CT. There is no other way of knowing how much fuel you have left. Lots of things can cause fuel depletion at a higher rate than expected. I forgot to replace a fuel cap once and lost a lot of fuel from that wing very quickly. Only the sight gauge told me there was a problem.
  2. The CT has very little dihedral which makes it more sensitive to fuel flow disparities then most other aircraft.
  3. The fuel system has only OFF and BOTH settings so the fuel can cross-flow from one wing to the other.
  4. The primary issue with uneven fuel flow is coordination. As long as you are flying coordinated, even if one cap is getting slightly more ram pressure or one fuel line has slightly more pressure drop, the cross-flow between tanks will tend to level things out.
  5. Coordination is a little different than "wings level" as was mentioned by others. As long as you fly coordinated during your turns about a point, for example during your search, the fuel will flow evenly.
  6. Coordination is a matter of degree. You may feel like you're flying coordinated, certainly good enough to pass a flight review, but you may be a little off. Your ball may even be centered but, as others have pointed out, they are not perfectly accurate either.
  7. The flow disparity, or cross-flow, is proportionate to the degree of un-coordination. In other words, the further the ball is off center the faster you're going to have a problem.
  8. The fuel distribution is an integration of the flow disparity over time. In other words, flying uncoordinated for a short period of time doesn't matter, but trimming the plane out uneven on autopilot does. I suspect uneven fuel distribution is much less of a problem when the aircraft is hand flown as you are more likely to be off one way and then the other more or less randomly, at least if you're paying attention.
  9. Turbulent conditions will also cause less of a problem as the fuel in the low wing will slosh over the outlet port at least occasionally.
  10. The effect of un-coordination is magnified as the fuel level decreases as the fuel in the wing with less fuel is likely leave the outlet port uncovered more often.
  11. You can only accurately check the fuel distribution when the ball is centered.
  12. The solution to an uneven fuel distribution is very simple: fly with the ball on the side of the wing with less fuel for a while (but not to such an extreme degree as to loose fuel out the vent). center the ball every once in a while to check progress.
  13. If either sight tube does not show fuel when the ball is centered, you should land immediately.

Mike Koerner

Link to comment
Share on other sites

I agree almost completely.  Mike says the same things but he says them better than I do.

 

Where I would change the above slightly is on step 12.  Returning to ball centered to check progress is likely returning to the unbalance that got you an uneven flow in the first place.

 

Instead of returning to ball centered to check progress or to continue flight after balance has been restored, first find the true balance point where the ball is off center but probably still in the cage.  You do this with the ruder.  A bit off left rudder to see how that changes the levels followed by a bit of right rudder to see the other change.  You can find balance easily this way and its far more helpful than ball centered.

 

The time to fly in a slip intentionally is when you have exhausted the fuel in one side. With one empty and one low fly in a slip so both you and you engine can see the fuel, this is not a time to slosh it to the outside and unport it.  When you say that remaining wing get critical its time to land, on a suitable road or susceptible field.

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.


×
×
  • Create New...