Do you know your safe approach and landing speed, and do you increment it for the prevailing conditions? Read on to find out what this means
I’m just going to add some more speed for the turbulence, plus some for the crosswind”. He gestures to me and adds “…plus throw in a few more for my fat passenger, and another five knots for the wife and kids.”….
Student pilot
Meanwhile the pilot forgets why they have added all the speeds, and ends up simply flying way too fast to ever consider touching down in the first half of the runway.
I look across, and I can already see that his plan is about to include pushing forwards on the controls, throwing out an anchor, standing hard on the brakes, and hoping that the new airfield concrete fence is a bit rubbery.
“Go around!” I demand, and before the puzzled pilot can figure out just how to do that, I’ve taken control and sorted the aircraft in a safe climb, ready for a more organised approach.
Don’t get me wrong, incrementing your approach and final speed is a valid and safe thing to do, but let’s not blindly add ten or twenty knots to every approach in the blind belief that faster is always better. Let’s consider some factors, and think about when to adjust for them.
WEIGHT
The heavier your aircraft, the higher the stall speed. Chances are our light aircraft won’t change much more than 150kg when fuel and the passenger is accounted for, and perhaps that won’t adjust the stall speed by much.
CONFIGURATION
Do you always land with full flap? Have you decided to land with only half flap, or flapless? If that alters your stall speed, then you will have to add the difference.
If it’s quite windy, with gusts, you may decide to land with less than full flap. Not only to retain better flight control, but also better enable your go-around when it’s required. Note that you will have to increase your speed for this new configuration, because of the change in your stall speed.
Many pilots these days are spoilt with tricycle undercarriage aircraft and can get away with a lower level of landing proficiency, however anyone who has flown tailwheel will tell you what happens when you try to land a taildragger too fast or too hard on the mains first… it just doesn’t want to land and this can often send you back in the air with a bouncy go-around!
DAMAGE
If your aircraft has suffered damage, like a birdstrike, or midair collision with another aircraft, or perhaps struck the Rugby Goalposts during the Workplace Christmas Flypast Lollydrop, then the aerodynamics are definitely going to change for the worst. Under all of those conditions, it is recommended that once you have safely climbed away from the ground, that you consider conducting an Upper Air Handling Check, to assess the controllability of your aircraft. You are going to progressively fly slower and slower down towards your normal flapless approach speed, and confirm that there are no unpleasant characteristics.
You begin to notice early stall cues, or begin applying lots of controls to stay straight, then power away and use that new speed as your minimum final speed. Why flapless? Because the last thing you want to do is to change the structure of the wing – those flaps may be the only thing holding the wing together. Also, if the flaps were selected, they may come down asymmetrically, which will guarantee you a loss of control – with a rate of roll that Red Bull Air Racers would be envious of.
RUNWAY ENVIRONMENTS and WIND
What is upwind of the runway, or even to the sides? Imagine the airflow before it reaches your aircraft, and try to guess what the effects may be.
Are the tall trees and hangars on the upwind side likely to cause turbulence?
Is there a massive slope below the threshold that will likely have downdrafts on approach, sucking you down with it?
Is the far end of the runway followed by a large drop, likely to force eddies and turbulence, and even airflow reversals down towards your landing area?
Are the two windsocks providing conflicting information?
Can you see evidence of downdrafts by strange patterns of dust?
Is the runway slope excessive, and am I going to require another few knots to raise the nose an extra eight degrees higher in my flare?
INTELLIGENCE GATHERING
If you’re new to the runway in question, talk to others who’ve flown in there before. Read up about it’s peculiarities. Use your radio and chat to the pilot who just landed. Orbit overhead, look at the windsocks, and note the direction that large cows and tractors are being blown in – and think about going elsewhere if there’s any doubt.
Landing speed example Example
Lets say for the mythical JORGOBEAR aircraft, this requires a 3kt change. So instead of my standard 60kts threshold speed, I’m now aiming for 63kts.
Remember, depending on whether the gust is or is not present at the point of landing, this may increase your groundspeed and landing roll – so you need to account for this increased speed and distance required for the worst case scenario (i.e. the higher groundspeed)
In gusty conditions, your IAS will likely bounce around, with the worst case being a sudden loss of headwind and a reduction in airspeed leading to an exceedance of the critical angle of attack and a potential stall condition. How do you compensate? Add an appropriate amount to your final speed – generally about HALF of the change in Gust amount.
If the wind is steady at 10 kts, but gusting to 18kts, then apply an extra HALF of the EIGHT knots gust amount (ie +4). Good airmanship dictates to also consider a personal maximum amount of Gust Factor (say 10 kts) you can accept – or else one day you mind end up flying at Vne through a hurricane!
So I’ll add the Gust factor 4 kts to my 1⁄2 flap threshold speed, which now totals 67 kts. Am I going to fly 67 kts all the way from Base, down Final, over the Threshold? No way José, that’s way too much hard work, and I’ll also cause irritation to my buddies following in their Lancairs, Migs and Learjets.
I’ll fly the usual higher speeds for those legs, taking care not to exceed any other speed limitations (like Gear and Airspeed limits), and I’ll verbally remind myself by saying out aloud, that I’m aiming for stabilised approach with “67 knots at Threshold” as I’m rolling out on Final at 500ft.
If I cannot establish a safe trend that will see me within 5 kts of that selected speed, then I will initiate a go-round, and set myself up for something or somewhere else, ignoring the loud laughter from the experts on the Aero Club verandah.
Conclusion
Not every approach will be the same, due to varying aircraft weight, configurations, potential damage (eg bird strike or overstress), approach and landing terrain or runway environments, and wind conditions.
Generally, pilots increment landing speed in gusty conditions by adding half the gust factor to approach speed, but it is a requirement to ensure your landing distance and ground roll are appropriate so that landing performance is assured.
Remember PRESS-ON-ITUS, and don’t fall victim to it. Do consider these factors, and come up with a sensible reason for intelligently incrementing speed to your approach and threshold speeds. Check your Aircraft Manual and Original Equipment Manufacturer’s recommendations, Company SOP research the changes and suggested speeds, and of course discuss this with your qualified flying instructor before doing anything new in your aircraft!
Aviating safety means mastering your speed control, both on landing and on take-off – this is especially important in the case of an engine failure after Take-off! However, maintaining a safe airspeed is just one part of how to make the perfect landing.
