This is for all of you who want to attempt to fly at extreme
altitudes and have never made it past FL400. Now I know that a lot of
you have read my article on
Tom Goodrick's XAS and have
downloaded it
and flown it (my mailbox is a testament to this) and have asked me
how to get to the altitudes that it is designed to fly at. And a
limited few of you have a copy of my ongoing XB-70 Valkyrie project
and there are those of you who have followed the progress of this in the
FS98 Forum and are probably saying to yourself "How do they get
to those altitudes and why can't I?" Well, pour yourself something to
drink and prepare to learn how some of us get to those mind-boggling
altitudes.The first thing you will need is an aircraft that is capable of reaching altitudes in excess of FL500 and there are a few to chose from. You can try my "Lady Hawk", Tom Goodrick's XAS or try some of the U-2's here at the site or you can try some of the SR-71's that are here. Once you have the aircraft that you want to attempt high altitude flight with you will want to take it up and fly it at lower altitudes to get used to it. This will come in handy when you do head for the stratosphere and get into trouble. Take the aircraft out and really fly it. Stall it and see what it does as not all aircraft simply drop their nose and start flying again.
Take it through a series of turns, both at low speed and at high speed. See how it handles during a climb. Basically you want to wring it out and become aware of its handling characteristics and any quirks that it may have. After you are comfortable with the aircraft you are ready to head upstairs (you stick and rudder boys may want to pack an extra box of tissues just in case).
As you get higher you will want to decrease your rate of climb. The reason for this is a simple one--you are running out of air. Air over the wings and air for the engines, both of which are a critical item.
As the air thins the push from the engines decreases. Even though the
gauges say you are flat out generating horsepower, the engines and
wings have not a whole lot to work with. And to get to high altitude
you need to maintain airspeed. At the cruising speed of the XAS at
cruise altitude you are just about 30 kts above stalling the
aircraft. At maximum speed you have about a 50 kt window. To maintain
the airspeed and still reach the cruise altitude you need to lower
your rate of climb. You will want to start this at around FL600.
Another point to remember is that even though you are on autopilot you still have to manually stop at any flight level above FL630. This is a quirk of Flight Simulator and don't ask me why because I don't have an answer and have never got one from Microsoft.
You want to level off as slowly and smoothly as possible to avoid stalling the aircraft or compressor stalling the engines. Your first clue that you are leveling off too quickly is the engines surging. If they start to surge, slow down your VSI adjustments and let the engines settle down. If you don't you will stall them and you will definitely have your hands full (and maybe your diaper too) as your power plants just became noise makers. If you incur a compressor stall pull back on the throttles immediately and push them back to full open and let them stabilize if they will. If they don't you will have to disengage the autopilot and gradually push the nose over and head down to thicker air to get them to straighten out. You want to do this slowly and gradually as not to cause a high speed departure which is caused by a sudden loss of airflow over the wing surface which means your airplane is no longer flying but is in fact falling. You will have to refer to the "read me first" file of your selected aircraft to see what the cruise at altitude settings are and adjust accordingly.
Now that you reached your first stratospheric cruise and everything is settled down nicely it's time to take a look around. If you are over land you will notice that a map is useless baggage, as you cannot really see any landmarks to fly VFR by. When you make a course change at this altitude you want to let the autopilot do it. All you do is tell the autopilot where you what to go. If, and I use this loosely, you want to try and take over and fly manually (this is a weakness of the stick and rudder gang) the following is a must heed, All control inputs are to be done slowly and gradually. I will repeat it, all control inputs are to be done slowly and gradually. Everybody got that? Because you are so high and the air so thin any sudden control input can and in some cases will cause you to lose control of the aircraft and it will take a lot of sky to regain it if at all. This is especially true of delta wing and canard aircraft. Anybody who has stalled a delta winged aircraft will testify to the sudden tip roll and nose dive that is an inherent trademark of the design (B-58, XB-70, F-102 & 106). A canard aircraft at lower altitudes is a forgiving airplane, as anybody who has flown one will tell you. At altitudes above FL700 the same sweet forgiving airplane can turn into a real monster and if you are not ready for it (hence the get used to it period) and you might find yourself on a head-on collision with terrafirma.
When you make a turn at high altitude and high speed be prepared to
use up a little sky. If you are a full time sled (SR-71 "Blackbird")
driver you already know what I'm talking about. If this is your first
time at high altitude you need to keep this in mind. A right or left
turn at Mach 3 @ FL800 will take a lot of sky to accomplish. How much
you ask? Well, let's say you start your left turn as you blaze west
over Des Moines, Iowa, when you finish your left turn you will be
headed south well past Topeka, Kansas. And to do a U-turn you will
come out of the turn headed east around the Oklahoma/Texas border.
This is not a misprint or a falicy, but a very true statement. You
need to plan your flight very carefully to get where you want to go.
Also, high angle bank turns at this altitude are a definite no-no as
the nose has a mind of its own and will head for the ground (the loss
of lift thing). Most of the time I try to plan my flights in a
straight line using GPS control of the autopilot as it saves fuel and
time and because you are above all the traffic there is not too much
to worry about in the way of a possible collision (unless you find
another sled driver).
"The Mutt"
muttly55@hotmail.com