Regular readers will know that I believe a good landing doesn’t simply happen in isolation, nor will it happen every time you land the aircraft. Rather, to ensure a good landing, fly a good downwind, base and final. To that end, recent training articles have been discussing tips for the circuit, slowly building up to the complete circuit picture. I have discussed the landing, flare and final approach, avoiding the banana: now this month let’s have a look at the base turn.
What is the base leg trying to achieve? The aim is to position the aircraft on final at the correct height, speed and configuration for the landing. Each aircraft is different, but a final altitude target of approximately 500 feet AGL at the correct aspect is usually about right. So we have 500 feet to lose on the base leg from circuit height. Although as an ex-military instructor I’m used to a continuous turn around base, the more common square base leg is flown with same underlying basic techniques.
Right, you need to slow down and go down. On downwind, at your base turn point (BTP), we need to get these two happening. Firstly, have your lookout complete before you reach your BTP. Don’t stuff about trying to look for other aircraft at the actual point, as by the time you’ve completed an effective lookout you’re likely to be five or 10 seconds past your turn point. Additionally, look in the correct area of the sky – in other words, where you are going, not where you’ve been or somewhere completely irrelevant like above and behind you. Believe me, I’ve seen this happen.
So, lookout complete, commence the turn onto the base leg 90º to the final track. If your aircraft requires it, configure. At this point, power controls your ROD (Rate of Descent) and attitude controls airspeed. So, hold the airspeed by holding the attitude constant and reduce power to begin the descent. How much height do you need to lose? How long does the base leg take? I have seen students begin a 90 second base leg and turn onto final, with 500 feet to lose, with an initial ROD of over 800 feet per minute. This is clearly not going to work. An initial ROD of between 400 and 500 feet is plenty, allowing you to adjust at the half way point to correct your profile. Get the aircraft settled early in the turn with the correct parameters set and the rest of the turn will come easily.
What are you looking at around base? Avoid staring at the threshold – remember that your ground track along base is further than the direct distance to the threshold. This can result in the feeling of being initially high on profile. If you subsequently increase your ROD to compensate, you may find that you are low when approaching the turn onto final. You must look for and find an appropriate point on the extended centreline as your final turn on point. It is overhead this point that you need to achieve the nominal 500 feet AGL and, something students often forget the first few times, be pointing in the right direction. Assess your glidepath to overhead this point, not forgetting the turn in, and glance at the threshold every now and then, if only to assure yourself that it’s still there. Once you approach final, take the threshold and runway aspect and aim point into your scan.
Don’t forget the correct base technique is Power for ROD and attitude for airspeed. Getting slow? Then lower your nose, re-trim and adjust power to keep the ROD constant. This technique changes on final – attitude now controls aim point and power controls airspeed.
Remember the effect of wind on your ground track and the time it takes to fly the base leg. A 20 knot wind blowing you out of the circuit will increase the time of the base leg by increasing the air miles flown. Therefore ROD will have to be reduced. The turn onto final will have to be initiated later and a drift correction applied once on final. A wind blowing you into the circuit requires a higher ROD (meaning less power) and more anticipation for the final turn in.
If it has been a while since you have practiced circuits, or it’s a nice windy day with a good crosswind, don’t shy away from practicing a few circuits at the end of your flight. Practice makes perfect, and a well executed circuit at the end of a flight is a sign of a professional at work. Grab an instructor and get into an aeroplane – it’s worth it.