Preparing for your first HP flight
Bob Kuykendall 5 December 2000
In a recent e-mail exchange with a new HP owner, I started to write up a set of recommendations for a pilot's first flight in an HP sailplane. Having had this experience twice (once each in my HP-11 and in a borrowed HP-18), I feel sort of qualified to make some broad recommendations.
Note that this treatise deals with a new pilot's first flights in a proven HP sailplane. It specifically does _not_ deal with flight testing or first flights in a newly-constructed or newly-modified and unproven sailplane. That's a whole different kettle of fish.
No doubt about it, preparing for your first flight in an HP/RS-series sailplane with large-span flaps is a challenge. In this situation, most sailplane pilots are faced with a situation where they will be exposed to an entirely new glidepath control tool (those large-span flaps) at the same time as they are exposed to an entirely new set of stimuli. The result cannot fail to be a situation with more than a little apprehension to it.
To begin with, remember that the large-span flaps are not a problem in and of themselves. They are easily the most effective glidepath control mounted to any modern sailplane, allowing near-vertical descents and approach glidepath control down to something on the order of 3:1. Flaps reduce the stalling speed, instead of increasing it as spoilers and dive brakes do. Flaps can also be used to adjust the airfoil camber for more efficient high-speed cruise. And, important in a homebuilt sailplane like the HP/RS ships, flaps are easy to construct and maintain, and can be actuated with simple and reliable mechanisms.
The problem with large-span flaps for glidepath is simply that there is no common and easy way for one to be instructed in their use, since almost all such flapped ships are single seaters. Sure, there are some specific exceptions. The RHJ-series sailplanes are basically two-seat HPs. So of course, if you have an opportunity to do some familiarization flight in an RHJ before flying your new HP, then run do not walk in the direction of that opportunity. However, the number of RHJ sailplanes in the whole world is a single-digit number, so such opportunities are few and far between. Also, note that not all RHJs have flap controls available to both pilots, so it is possible that even in an RHJ you will not have an opportunity to practice all phases of HP operation. At least not without a very trusting RHJ operator at your side!
Before you embark on your first-flight experience, you will certainly want to read the original "Flight Testing" article for your ship, if there is one. These articles are usually "bulleted list" recommendation that Dick Schreder put together for the original HP builders newsletters. However, as terse as they are, I have seen few accidents that would not have been avoided by following them.
For the HP-11, -14, and -18, see:
For other models, see the article for the ship with wings most similar to yours. For RS-15 or HP-16, see the article on the HP-18. For the HP-12 or -13, see the article for the HP-11 or HP-14.
Of course, the most important thing about your first flights in an HP is learning to effectively use the large-span flaps for approach and landing.
Remember that, when applying flap settings above about 30 degrees, you must aggressively lower the nose to maintain flying speed and avoid stalling. With full flaps, the deck angle required to maintain flying speed can be somewhat alarming. I have never measured it, but I suspect that it is on the order of 45 to 50 degrees below the horizon, and you will be looking through the top of the canopy at the horizon.
To keep from losing airspeed when applying large flap deflections, you must lower the nose at the same time as you are extending the flaps. If you extend the flaps first, and then adjust the pitch once the speed starts bleeding off, you will find it rather difficult to regain the lost speed. It is much better to learn to make both adjustments simultaneously. Even if you aren't sure how much forward pressure to apply to the stick, it is better to start off with some increase in forward pressure and refine it later than to apply none at all.
At large flap deflections, it is very easy to shed speed, but very hard to get it back again. This makes full-flap landings rather tricky, since energy dissipates very quickly once you start to flare. If you start the flare too early, you can easily get too slow and mush into the ground. Your best bet is probably to arrange your first landings so that you use no more than 60 degrees in the approach, and keep flying speed right into the flare.
Also, remember that adding flaps adds lift as well as drag. Consequently, if you are landing and in ground effect and you add a little more flap, you will balloon up unless you simultaneously add some nose-down pressure on the stick. This is an important thing to watch out for. With practice, you can compensate for this tendency with subtle pitch adjustments, and make late additions of flap look smooth and natural.
Also important is that you should be very careful about retracting flaps while landing. Some pilots may tell you that you should never back off on the flaps while in the approach. However, the consensus seems to be that you can carefully retract the flaps in the approach as long as you do it smoothly and in moderation, while simultaneously applying pitch inputs to keep the airspeed where it belongs.
Another thing to watch out for is that slipping with a lot of flap extended will cause the nose to lower slightly, and will feed some funny shakes into the control stick as the flap wake hits the ruddervators. This can feel alarming, but is probably not dangerous. However, you should avoid slipping with flaps until you are more familiar with the ship.
Regarding the flap control itself, it is difficult to make any specific recommendations, since there is a wide variety of controls fitted to various HPs. Some ships have cranks, others have levers or hydraulic pumps, and some even have simple sliding handles that require a mighty heave. Whatever the system in your ship, you should be able to find the handle blindfolded. For hydraulic systems, you should also be able to find the release control without looking. For the crank systems, you should know which way to turn the handle for both extension and retraction. However, don't worry too much about getting flustered and forgetting which way it turns. In most cases, the handle turns against the resistance of the air loads to extend, and with the resistance of the air loads to retract.
List of Recommendations
The first flight is the most troublesome aspect of learning to fly an HP. If for some reason you must land the ship before you have a chance to learn its traits (for example, if you have a rope break or early release on your first launch), you will be immediately placed in a very demanding flight regime in which you have very little experience with the tools at hand. For this reason, I recommend:
1. Unless you are very experienced, you consult with a qualified CFIG before your first flights, and afterwards to debrief. The CFIG should be one you've flown with, so that they know your strengths and weaknesses. Ideally, the CFIG should have some HP experience, but that is hard to find in a CFIG these days.
2. Carefully choose a flying site with long smooth runways and lots of options for rope breaks or other unexpected situations.
3. Validate the aircraft weight and balance data before the first flight, or at very least make sure that you fly the ship with the same weight and balance condition as it has been successfully flown in the past. This can be as simple as making sure that you have the same cockpit weight as the previous owner flew with. However, if you have made any changes to the ship's CG situation, you should at least recalculate the CG envelope, and probably ought to do a full weighing. I had trouble with this on my first flight in a borrowed HP-18. According to the placards, I was well within the allowable CG envelope. However, due to suspected W&B irregularities (and perhaps control system slop), with me in it the ship was so tail-heavy that, with 60 degrees of flap the stick was at the forward stop at 50 kts, and more flap would have caused the nose to rise further and the ship to stall. Not fun.
4. Give the aircraft an extra careful pre-flight inspection before the first flight. Make sure that all pins and controls are connected and safetied, and that the ruddervator drive angles are properly seated in their pockets on the drive arms.
5. Test the airspeed indicator before the first flight. Just make sure that when you very gently apply air pressure to the pitot tube, the needle on the ASI advances up the dial, and does not retreat until you reduce the pressure. Because of the flaps, you cannot easily judge your airspeed by the position of the nose against the horizon. This places great emphasis on the airspeed indicator for the first flights. Later, you will learn to integrate information from the flap position, deck angle, cockpit noise, and other sources to gauge your airspeed. But for the first flights, test the ASI before each flight to make sure that no bugs have made their homes in the pitot tube. I know from first-hand experience (on my second HP-11 flight!) that there is a type of insect at Minden that can completely block a pitot tube with leaves and eggs in less than one hour.
6. Make your first launches in smooth, calm weather conditions.
7. Engage the services of a fast, nimble, well-trained wing runner for the first flights.
8. Consider leaving the landing gear extended for the entirety of the first flight. You will have more important things to worry about in dealing with the flaps. The extra drag of the extended gear won't make that big a difference, and it will be one less thing to worry about.
9. Test the tow release before the first flight, and gauge how much or how little back pressure it takes for the hook to back-release the tow ring.
10. On your first tows, you take special care to allow no slack in the tow rope so that you don't accidentally back-release off of tow. You may find that keeping about 10 degrees of flap on tow will make it easier to keep positive pressure on the tow line.
If you have an HP with non-interconnected flaps and ailerons (most but not all HP-11 through HP-14, some HP-16, some RS-15), taking off with modest positive flap will have little or if any effect on the roll control. If you have an HP with interconnected flaps and ailerons (all HP-18, many RS-15, some HP-16), roll control on takeoff will be best with negative flaps. However, going from negative flap to positive in the takeoff roll takes a lot of attention that might better be spent attending to things like getting ready to release in case of a ground roll excursion. You will have to decide for yourself whether to take off with negative flap and sacrifice some attention, or to takeoff with positive flap and sacrifice some roll control. Consult with your CFIG about this.
11. Tow to at least 4000 AGL on your first launches, with the first priorities on:
learning the stall behavior at various flap settings.
learning the overall behavior of the ship at all flap settings from full negative to 90 degrees. Explore the full-flap behavior as early as you feel comfortable with in the first flights. Later in the flights you will have less time and altitude to explore this flight regime.
learning the necessary coordination between pitch inputs and flap inputs so that you can do them simultaneously or nearly so without thinking about it.
learning the general "feel" of the aircraft regarding control pressures, cockpit noise level, and instrument behavior.
12. Formulate an emergency plan in case of difficulty on the first few launches. The first part of this plan should be "fly the aircraft and stay in control." The canopy pops off. You hit a bird. The radio quits. The gear gets stuck. The rope breaks. What do you do first? First, fly the aircraft, keep your airspeed, and worry about the incidentals later.
The hardest thing to plan for is what to do if you have an early release. You should have a plan for what to do with the flaps in that situation. You might consider something like going immediately to 30 degrees of flap while simultaneously lowering the nose, and then treating the flaps sort of like dive brakes from then on. The first 30 degrees of flap mostly adds lift, and the next 60 degrees mostly adds drag. That is sort of an oversimplification, but for the purpose of a first-flight emergency, will be better than nothing. Talk this over with your CFIG.
These are my opinions only based upon the operation of my own HP-11, and upon my first-flight experiences in HP-11 and HP-18. You should consult with a qualified CFI before flying your own ship.
What other say
I originally circulated this article on the HP-Gliders Internet forum, and invited the listmembers to add anything they thought appropriate. Many members did add some valuable insights in followup messages. Below is a sampling of their input.
Here are some other points that I made on this same question a couple of years ago:
1. On a no-wind day you should have the ability to turn final, set the glide-path control, and then land on your chosen aiming point without further adjustment. If you need to play with the spoilers right down to the flare even in no-wind condition, you are going to have a high workload in a HP.
2. Don't mess with the flaps during the flare on you first flights. Set up the approach such that ~45-55 degrees of flap will put you on the runway, then leave them alone (see point #1). Don't worry about landing in the "preferred" location or next to your trailer, between the fences is just fine for the first flights. Later you can try approaching with less flap and then adding more at the flare (approach angles similar to spoiler ships), or approaching with more (eye-poping descent angles, but timing of flare is more critical.). One trick you can use if you are using the shallow approach method is to take advantage of the natural "pitch-up" tendency of the flaps to flare for touchdown. Instead of flaring with elevator then adding flaps, flare with flaps and use elevator to control the rate of flare.
3. Don't approach faster than necessary as you will burn up 100's of feet of runway in the float as the ship refuses to settle in. If you try to force the landing then the ship will bounce. (Remember it's *much* easier to bounce with a tail-dragger.) I was told on my first flights that if I bounced then keep the wings level and go along for the ride. I have since worked out a strategy for handling bounces, but it has a *VERY* high workload (flap full negative until ship stops rising then full positive until second touchdown then full negative, all while maintaining proper airspeed).
4. Don't try to taxi until you've made a few landings. Tail-draggers are easier to ground-loop.
But by far the biggest problem is people saying "Flap-only ships are difficult to land". They're *different* but not difficult, and the lack of a flap-only two-seater means you have to learn from confidence in you abilities and experience. Most of the so called "experts" have never flown a flap-only ship, they've just heard the "horror stories" from people who have tried to fly them without first asking for advice.
Another good exercise would be to do some patterns in a Ka-7. These have VERY effective spoilers, and you can simulate the braking effect of flaps to a certain extent. Set up a little high and fast, (60 or so mph) then use a lot of spoiler. Work to keep your target speed, but be careful not to get too low. You will find that the nose has to be dropped to a surprising degree, and it just doesn't pick up speed. Good practice. It won't float like a flapped ship though, unless the instructor comes off the spoilers as you flare. If you aren't use to a really reclining seat, you may have some trouble in the HP-14 and -18 with attitude and and airspeed control at first. Again, find a two seater with a similar seating position and go flying. Strangly, a good place to start is the back seat of a Twin Astir (the ones with retractable gear). You are sitting over the landing gear, so the seating position is very much more reclined than one would expect.
A few hours of dual in a Cessna 150 or 172 would not be a bad prep for learning the fly approaches with Flaps. These airplanes have large enough flaps that they can demonstrate the steep deck angle required and approach path simlar to an HP, with the comfort of an instructor next to you. It isn't quite the same but it certainly will give you some more experience to draw upon during the 1st flight of the HP.
Sitting in the cockpit and noting the position of the horizon line (if available) with respect to the canopy/instrument panel could be helpful because this will be about where the nose will be at touchdown. As you know, with a good bit of flaps cranked on the nose is considerably lower. This will give you a feel for how much you must raise the nose as you flare.
Be mentally prepared to adjust your "flight plan", if needed. Planning to take off and tow with zero flap and land with 45 is fine until execution shows that it doesn't work very well. In the '18, for instance, I find -10 flap essential for control any time the tail wheel is on the ground and +10 nearly essential to keep the tow plane in view.
Choose a time that is very quiet at the field. The subtle (and not so subtle!!!) pressure of getting going when there are others waiting to launch is something that you will not need. All your attention needs to be on the task at hand and not on someone else's issues.
Arrange to sit in the aircraft with the tail raised to flying position and the wings level. Spend some time with the tail raised even higher to get the feel of landing (or approaching roundout). This attitude is very easy to get used to, in my experience, but sure is a surprise if all you have flown before are non-flapped aircraft!! Mentally picture the coming flight and go through the motions of moving the controls. Visualize what might go wrong and decide now what your response will be. Discuss your choices with a qualified instructor. The idea of these exercises is to remove the surprise factors and let you 'fly the aircraft' under pressure.