Advanced Pilot Programs - The Stabilized Approach
Last Updated: March 14th 2006
THE CONCEPT OF THE STABILIZED APPROACH.
Hello, and "Welcome back". I hope you have enjoyed my "Emergency Series". We went over a lot of material in those four scenarios. In this presentation I am going to explain the concept of the stabilized landing approach. Here is an overview of what we are going to discuss.
Most Airline Crews have a set way of doing an approach to landing. If both pilots know the procedures than each can expect certain things to happen at a given time. If something were missing, then this would trigger a suggestion by one of the pilots to address the subject. This has to do with the concept of "cockpit communication and crew coordination". At least two pilots, and sometimes a flight engineer, are on board to prevent the start of the so called "error chain".
On the descent and landing checklist we need to look up the "Vref" speed for our landing weight and flap setting. Please remember that "Vref" is the landing speed that we will fly and it is 1.3 times the stall speed in the "landing configuration". Believe it or not, most of the time, this speed is a constant. Airlines put enough fuel on the airliners to comply with the FAR's (Federal Air Regulations) as to trip fuel requirements. Performance suffers if you "tanker" fuel (carry fuel you don't need). So the landing fuel weight is almost a "given". The only variable would be passenger load. Airlines go into great statistical efforts to know the passenger load for each "leg". Putting the two together gives us the weight for the "Vref" bug speed.
There are certain things that will add to this "Vref" speed. If we had an engine shutdown or were landing with reduced flaps or no flaps at all, then this would add to our "Vref" number. Also, if the ATIS gives a wind condition of "gusting" at a certain speed, then this would add to our speed. You figure this out by taking one half the gust factor and adding it to your basic "Vref" speed. You would do this up to a maximum of 10 knots added. Any more than 10 knots above basic "Vref" would increase your landing rollout distance too much. A good airline pilot may also add some extra speed if he suspects a condition of "wake turbulence" or possible "microburst" activity. I am going to go into details on both of these subjects in a later article. For now let us just say that "wake turbulence" is the spinning "wake" you might encounter if landing behind a larger airliner and "microburst" activity has to do with landing shortly before or after a thunderstorm condition. So to "recap"; our "Vref" calculation is determined by 1.3 the stall speed of your airliner with full flaps and at landing weight. Now if you get an ATIS or a report by a voice controller of something like this: "wind is 230 at 10 knots gusting to 20 knots" you would add 5 knots to your base "Vref" speed and fly your approach using this new "Target Speed". If the wind were not gusting, then you would fly your approach at "Vref".
The concept of the "stabilized approach" is to have the gear and all flaps in the landing configuration before you hit the final approach fix (for example let us use the "outer marker"). What we are looking for is that no other configurations will be applied as we descend on the glideslope after passing the OM. Most real airline approaches (IFR) are flown using the autopilot to "mins". Using the autopilot allows the crew to become "systems and approach monitors". The Pilot Flying (not necessary the Captain) has his hands on the yoke but allows the autopilot to fly the airliner to the preset "decision height". Some "old timers" still try and "hand fly" the airliner on the approach, but this is not the preferred way. When you are outside the marker inbound get your flaps down to "approach flaps". As you get closer to the marker you will see the glideslope needle coming down to the intercept "cross hairs". When the glideslope needle is "one dot above" call for the "landing gear down" and get your flaps to the landing configuration before glideslope intercept. Also make sure you are at your "Vref" speed as you cross the marker and get glideslope intercept. Now, you are set for that "stabilized approach".
Flight sim has a bad feature in that; when you are set up for the "stabilized approach" you will still get an extreme dip at intercept if using the autopilot. In the real world this is not the case. It is something that I have "lived with" in my VA computer flying. Maybe the next version of Flight Simulator will improve upon this shortcoming. Another trick, that I have used, is to put the "min decision altitude" in the autopilot altitude select. This way I have a backup of what the "min descent altitude" is (if I forgot the Jepp approach plate DH altitude or I became distracted). One last trick, that I have used, is to put the heading bug on the initial missed approach heading (remember the autopilot is in the "approach mode"). This way, on a miss, I click off the autopilot and know what the initial missed approach heading is. Another good piece of advice is to declare a miss and "go around" if you feel that something is not right. Don't try to attempt to figure out or cure a problem as you are descending on the glide slope. Better to declare a "miss" and sort out the problem in a holding pattern. At your "decision height" or "missed approach point" you click off the autopilot and hand- fly the airliner for the remaining portion of the flight. If you are Cat 3 equipped then you can use the autopilot down to landing. For most of us (and unless your have a good autoland), DH (decision height) will be where you click off the autopilot for landing.
If you have to "go around" or "miss" on the approach the first thing you do is add power, then get your flaps to approach and then get your gear up when you see a "rate of climb" on the VSI. Perform your missed reconfigurations in this order. (Power, pitch, flaps, gear). Remember to fly your published "missed approach procedures" or clearance as received by ATC.
OK, by using all of the above you are all set to give your passengers a smooth approach and receive that well-earned respect from your flight crew.
Chief Administration Officer
Head Of Training
My thanks to Mark Chapel for "Proof"
NOT TO BE USED IN REAL WORLD FLIGHT. NO PARTS OF THIS ARTICLE MAY BE REPRINTED WITHOUT THE WRITTEN PERMISSION OF THE AUTHOR.