Sunday, May 6, 2012

Mockingjay

Finally got around to finishing the series.    Very bleak and absurd reading for a young adult series, but harder to objectively criticise in many respects to the earlier novels. 

Felt in a way like having ended on a Time bandit notes with the parent's having touched the 'rock of pure evil', but sometimes one wonders if there isn't this sad reality to life.

Recall another book Briar Rose by Jane Yolen...less visceral more subdued but still an excellent read.

Flight Sim revisited

Don't know how to land a Boeing heavy in Flight Sim X.

Quickest primer.

First off should mention that while Linux distros do have a flight simulator, not quite package ready like Microsoft's flight sim X, and if you were ever interested in Space simulator programs.  The best free ware program has to be Orbiter.

In any event, always recommend a fairly decent joystick likewise for control operations, albeit the potentially lifesaving primer that I give amounts to no hands on use of any controls what so ever.  This means you punch in the data, and let the plane's autopilot do the rest, but technically I could provide some visual flight instructions for typical landing here.

1.  Without charts or landing instructions.  Study the terrain map of landing location in advance.  Knowing the terrain means avoiding a stray mountain in advance especially where descent is critical.  Ideally making sure your altitude provides ample clearance here part of this.  Part of the fun of landing without navigational maps for descent instructions can be the challenge of figuring out a descent pattern to land at a given airport. If you decide to fly the a Heavy aircraft, the big jumbo jet variety.  Keep in mind some clues whether or not your craft is suitable for a given site are:

-How long is your air strip?  Preferably this is something like 10,000 + ft in length
-What sort of surface type?   Asphalt or concrete.

2.  Does it have a ILS transmitter?  If you don't have ILS the visual, hands on control I believe will be the case for landing here and you are probably out of luck finding some instrument based don't touch the steering wheel method here.

The generally rule flying heavy's here, I've found are:

- Major cities throughout the world with INTL airports generally host both ILS and the appropriate landing runways.  Flight from New York, NY to Memphis, TN will probably work, you could choose one of the shorter range heavy's for this hop, while a trans Atlantic crossing you will use the heaviest of heavy's 747-400 for example.

3.  Know how to use your aircraft's auto pilot systems.  Basically, this means being able to dial in your speed in knots at least,  and knowing how to dial in the aircraft's altitude.  Know how, to use a the heading switch, and dial in a heading course.  Know how to use the approach switch when the plane is in ILS range (ILS means Instrument Landing System), and know when ILS will typically be available...something around 20 nautical miles.

4.  Know your aircraft's flying specifications.  You should know the plane's air speed range limits.  This includes at a minimum overspeed, stall speeds, and approach speeds.  The heaviest plane typically has an approach speed of 155 knots with full flaps and gear extended although this varies depending on your plane's loads.  Generally I don't like to err with too little speed on approach since you may find more then likely your plane dropping out of the air stalling basically and crash more likely even if you think you close enough to ground not to result in major consequences.  So if you err with an added range of knots up, generally I like no more then 10 knots above approach speed, here.

5.  Double check your plane's configuration before making the landing.  Gears should be fully extended and so to the flaps, especially if you are using set approach speeds.  The flaps help keep your plane aloft at lower airspeeds without your plane will likely stall out.

So a basic checklist for approaching an airport is as follows.

6.  In a heavy if you 30,000 ft +  in the air I like to start descent at anywhere from 100 to 120 nm out from your destination airport, with a descent of -1800 ft/min.  Especially in the heavy's as it seems going any faster, seems to result in greater difficulties controlling airspeed without supplement air braking.

7.  I like to visually follow a radial pattern around the airport at a radial distance between 20 and 40 nm depending on what terrain provides here.  If you decide to use a non radial pattern for lining up with your landing strip, its best to turn in the direction that moves you away from the landing strip first, then turn in course in the same radial fashion until you are oriented in line with the airstrip.

-for example, you approach the landing strip with it to your left between 9 o'clock and 12 o'clock, then turn clockwise right, once the the strip is at least at your 9 o'clock position, or if the landing strip is to your right on your approach with its position bearing between 12 o'clock and 3 o'clock, then with a relative perpendicular approach wait until it is at your 3 o'clock and make a left turn turning counter clockwise until oriented in alignment.

Why do this?  In turning you don't lose approach distance while making the turn towards the landing strip overall when turning first in an opposite direction to orient your aircraft...think of it this way, if you are first perpendicular in approach to the strip and you move for the 90 degree radial range away from the strip, you will have netted zero distance to or from the strip if you turn another 90 degrees toward the strip at the same turn rate and overall airspeed.

8.  I like to have an approach altitude lined up at around 2000  and 3000 ft above the landing strips altitude.  Make sure you know the landing strips altitude.  You can find this alongside detailed ILS frequency and landing strip course heading on the Maps page of your flight sim.

9.  Dial in your ILS frequency for the chosen landing strip, and dial in the course heading...minding on the Boeing 747-400, I hadn't found a way to dial in course heading and as far as the auto pilot is concerned doesn't seem to matter.  On the others you just dial in where you have the course knob/switch.  Shift+2 to pull up the radio stack here, and you will need to make sure the ILS frequency is dialed in on the NAV1 or NAV2 radio stack.  You can dial in frequency on the right hand side of the radio stack and then press the '<-->' button, for example, on numerous aircraft to change frequency, by pressing this button you enable it on radio systems and it is toggled to the stacks left hand display side.

10.  Use your heading autopilot switch in conjunction with GPS navigation tools here.  Your GPS receiver provides a radial compass with course heading stamps relative your planes position relative your destination airport.  This should help if your visual sense is limited, owing to any number of factors.

Some basics of course heading.  You course is 270 degrees you turn to 0 degree your plane will turn right, if you slide your heading switch greater then 270 degrees towards 360 degrees or zero.  However, if you slide your switch in the opposite direction (less then 270 degrees) you will bank left toward zero in a counter clockwise turn.  

10.  Make sure your craft is generally lined up with decent room to spare if you can...ideally nice with jets to a 20 nm range from landing here, the more line up the better.  I've found the autopilot systems on board the craft oscillating more likely from the left to right of the airstrip but never quite stabilizing with too little distance to close for landing, so the less work you can make for on board landing systems the better.

On you final landing approach (less then 20 nm out from landing strip and lined up with the landing strip appropriately) do the following:

11.  Make sure you are parallel to the strip and lined up to intersect such strip with your course heading.  If the strip is significantly to your left or right but you are flying parallel, your autopilot approach systems may not be able to course correct and you may need to do this manually.  The way I like to do this is pick an imaginary point either visually, or with the gps pick a course heading in the direction that you need to move your plane to line up here.  The art of doing this, is to pick this such that the point is heading wise greater then the airstrip to intersect it, but neither greater then a perpendicular course relative the airstrip.

Thus if the airport is at 330 degree to your left and you are flying 360 degrees parallel to the airstrip.  You could pick any course correcting heading range from 330 - 90 to correct your aircraft, but keep in mind if you need you will need to bank your plane one you are on the correct approach course, back in the correct oriented direction to match its course direction parallel to the landing strip.  Ideally you may want to decrease the difference between your correcting course turn and the course that you need to be on before you intercept the course that you need to be on.  This is not unlike rolling your car out of its turn once your turn is completed.  Before you attempt landings with jets, I recommend practicing both with a stick and using heading controls, turns in a way that you are familiar with course correction...this means practicing, without attempting the land, turns so that you are a parallel and on course to intercept the landing strip from your position on the air above projected on the ground.   Its really a skill in most cases that's picked up with practice.  Keep in  mind if you decide to course correct overriding the on board autopilot approach navigation systems, your descent pattern for approach landing will be controlled by you as well, so it ideally you'd probably want to do any significant corrections prior to 10nm from landing, and ideally the range of necessary correction should require turns less then 90 degrees from your present course.

12.  Make sure your ILS is enabled by:  toggling the GPS to NAV switch (all Jets have this), and pressing the approach button on your autopilot console interface, I usually don't do this until you are on your final approach at least less then 20 nm.

12.  Flaps fully extended, airspeed in appropriate range, gear down.

-For the most jets you should be moving no more then 180 knots on this final approach.

-When autopilot landing be very careful with air braking, this can cause catastrophic loss of airspeed and lead to your plane dropping out of the air dramatically since it seems in my experience response times especially on the heavier of aircraft are slower relative to the increases in air friction and loss in air speed provided.  I don't recommend air braking with an auto pilot systems based landing at all here, until you are completely down on the air strip.   ILS descent schematics generally for landings are such to provide the aircraft a controlled descent that neither provides for strenuous work on the landing approach, this means neither gaining  much airspeed energy because of a rapid descent as a consequence, but a smooth, no airspeed gain while descending appropriately, so technically you shouldn't have to be air braking in many circumstances.

And above all make sure your approach speed is above stall speed at all times...you have a sink rate warning it means you need some thrust...for jets, you can add quite a bit rapidly and then pull back on thrust once the indicator moves in the positive direction.  Heavier non military commercial aircraft jets again have more latent thrust responses relative the lighter commercial variety. 

13.  I recommend manually controlling airspeed here, otherwise, you will need to disarm your speed controls and autopilot systems immediately once you touch down, to slow your aircraft down asap, with an air brake followed ('/' key).



Birch wood bed blender example

Friday, May 4, 2012

Older blog posts still lingering in rss feed land

Even formally at this site apparently older posts had disappeared previous to this year, you can still find older posts still floating around in rss feed land, you just need to subscribe to the blog as a rss news feed, and you should be able to access older posts that way.




Wednesday, May 2, 2012

Tuesday, May 1, 2012

Set intersections problem

Okay someone posted a set intersections problem, and asked what methods could be used for finding these.

One solution involves iterating the set, while iterating another set.  In python, however, I like to create dictionary keys to avoid creating a second loop iteration.

If keying all elements of a set (and there are one and only one such element of such set...not a list in otherwords), then you could check for set intersection creating an iteration on the first set and checking inclusion on the second set.

code:
for element  in set1:
   if element in set2:
      found intersection

Another method in more specialized cases:

If you have an ordered and quasi continuous set of element...by continuous or discretely continuous, by discretely continuous this means in python for an ordered pair (a,b), all elements of range(a, b+1) exist
in such set, or read another way, for an ordered pair (a, b), elements a, a+1, ..., b-1, b exist in such set and no element  c exists such that a < c < b where c is not in the set of range(a,b).  In this case, one can compare address range by the ordered pair (a,b) and another set (e, f) where if  a > e and  a < f or b > e and b < f or a < e and b > f, similarly one can compare the elements e and f with a and b.  This should at least determine if intersection on a range of elements exists without having to iterate each and every element of two corresponding sets.
Potentially if intersections do exist, this could be faster or slower then iterating all elements of a set if depending.  Potentially in this case, you could find within two calculation steps, or as many as the number of conditionals listed above through the full series of checks as compared to a total step wise calculation of the length of set1 * 2 adding the conditional in the previous case.  

I would mention method two is more advantageous when the smallest of two sets is larger then the step wise algorithm itself.   In this case probably exceeding more then say 6 elements.

Considering now an additional problem and solution using the second method above.  If you have a family of sets to compare in this set intersection problem where each set are ordered and continuous, then you could use keyed addressing range for all such sets, and eliminate through address determination your existing set in so far as its placement relative the others,  possible sets that could intersect before ever having checked for set intersection.  This would be useful in the case of high volume intersection searches.

Example of this in the one dimensional case on the set of positive integers J are:

addresses given as follow address_ranges = {'1': range(0,10), '2': range(10,20),...,range(n-10, n)} where n is some integer in the set J.

If you has an ordered set range(3,15), then addressing blocks in the keyed case above are '1','2' and any set in a family, keyed as '1' and '2' should be checked for intersection, while those outside such range are ignored.
 
If using block addressing ranges, keep in mind interior block addresses that coincide with other blocks need not be searched for intersection element by element here since all such interior points if a address matche coincides with another interior block at the same address. Why? Since if in constructing from a range several blocks where there exists block addresses a and c such that for block address b, a < b < c, implies b fills ordered and continuous points at address b.

example, consider as previously mentioned in the one dimensional case range(10, 45), then the following block addresses suffices, (1, 2, 3, 4) where block addresses: 2 and 3 are interior and elements at such block address exist in such such subset block range. While for endpoint block addresses 1 and 4 the same claim could not be made, at least we can say this for are range(10,45) whose block 4 range subset consists of elements (40, 41, 42, 43, 44, 45).

Oblivion

 Between the fascination of an upcoming pandemic ridden college football season, Taylor Swift, and Kim Kardashian, wildfires, crazier weathe...