• How To...Fly At High Altitudes

    How To Fly At High Altitudes And Make It Back To The Ground

    By Curt "The Mutt" May

    Introduction

    Tom Goodrick's XAS 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).

    High Alititude Basics

    The first rule of flying high is to let the airplane do the climbing. What to I mean by this you ask? What I mean is that with the exception of a very few aircraft you need to let the airplane do the climbing by setting the VSI gauge to the standard rate of climb for the aircraft and the airspeed and let it do the work.

    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.

    Lockheed SR-71 Blackbird 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.

    First Flight

    Now that you have you trusty steed of the heavens all sorted out and are comfortable with it let's head out to the active and head upstairs out of traffic (when was the last time you saw a 777 at FL600 or higher?) After you leave the ground (your pre-flight should already be done and the GPS programmed) and get settled in you will work strictly with the autopilot for both speed and ROC. You can maintain a standard 1800 fpm to FL500 with most aircraft. After FL500 you want to slow down your ROC to around 1400 fpm. The first thing you will notice is a decrease in throttle. This is normal and as you continue up at this pace the engines will come back up to maintain speed all, of which is normal. As you pass through FL600 you want to decrease you ROC to around 1000 fpm for most aircraft and maintain this ROC through FL650 when you will decrease your ROC to 500 fpm. You will want to maintain this till you reach FL700 where you will decrease your ROC to 200 fpm. Now if you are flying the XAS you will want to carry this through FL720 where you will drop you ROC to 100 fpm and carry this to your cruise altitude of FL740. Your speed for the XAS will be Mach .85.

    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.

    Lockheed U-2 Dragon Lady 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).

    Descent And Landing

    Now we all know that whatever goes up has got to come down, and when you are flying at this altitude it takes a little bit to come down and the higher up you are the farther it will take you to come down. It will take you about an hour or more to get to cruising altitude so you can figure it will take you an hour to get down. At Mach 3 one hour out from your landing is a long way out. To give you an idea, if you are on a straight in approach to ORD from San Fran @ FL850 and your ROC is set at 1000 fpm you will start down a little west of Grand Island, Nebraska. You will drop to sub-sonic around Lincoln, Nebraska still above FL750 and be in the approach lanes around the Iowa/Illinois border (the Mississippi River). Plan your flights carefully. If you are headed to an airport surrounded by large immovable objects (mountains or skyscrapers) you need to plan your approach to take them into account lest you become wallpaper on a building or a crater on the side of a mountain. You want to use the autopilot for the ride down until you are on your final approach, and if you planned a straight in approach then you have no downwind leg so you can manually fly down to the pavement when you get down below 10000 feet.

    Summary

    Now I've tried to cover the basics in this to help those who have not been able to fly above FL400 get to these altitudes safely and make it back down. At levels above FL900 and FL1000 things change again. As the information that has and is being gathered about this region is broken down and made understandable I will pass it along in another article. For now let's just say it is a really wild ride both on the way up and definitely on the way down (I know this first hand). It makes the wildest roller coaster look and seem tame and mundane in comparison. For those who wish to venture farther up, remember the basics and be ready for a rough ride down. For those who are content to reach and cruise above the normal airline traffic in complete comfort I hope this helps a little in your quest for altitude. If you have a question or two you can drop by the forum and ask it or you can send it to me via my e-mail link at our web site, which is sponsored by FlightSim.Com. The address is http://www.flightsimnetwork.com/phoenixflightserv

    "The Mutt"
    muttly55@hotmail.com