Sorry Diana dat ik het hier even volprop, maar misschien is dit voor iemand van interesse. Bij mij vergaren ze alleen maar stof op mijn harde schijf
BAD ATTITUDES
A simple way to manage
instruments for IFR flights.
You're screaming through the clouds at 120 knots. Visibility: 2,5 feet-the distance from your eyes to the windsreen. The only clue you have to where you are and where you're going is the dazzling array of gauges and needles slow dancing on the instrument panel. Your job: keep the airplane right side up and find a cloud blanketed run¬way some 100 miles distant and 3000-5000 feet below.
"Now let's see. We want a clim¬bing turn. So the attitude indi¬cator is primary for pitch as I begin the turn. No wait, is this going to be constant speed cli¬mb? Then it would be suppor¬ting. But that's only as I'm esta¬blishing the climb, after that it is suppporting. No, is that right?
Learning to fly an airplane un¬der IFR conditions is conside¬red by many pilots to be one of the true challenges of aviation. The fact of this is borne out by the require¬ments for the instru¬ment rating-40 hours of simula¬ted IFR or as much as the re¬quirements for the Private Pilot license.
As with all flying, our goal in instrument flying shou¬ld be to keep it simple. After all, if we keep it simple, then our work load is reduced. And if our workload is reduced, then we are less likely to get behind the airplane and into trouble. The ideal situation for the IFR pilot is just to monitor the airplane-its performance and systems-to make sure that everything is going right. Our job is easiest when we scan the instruments, find that the airplane is doing what we want it to do and don't have to make any adjust¬ments. This sounds great but how do we make it happen?
There are two skill areas that lay the founation of IFR flight. The first is basic attitude instru¬ment flying and the second is what one calls aircraft manage¬ment.Master these and your ability to monitor the airplane improves greatly.
The generalized concept of ba¬sic attitude instrument flying includes scanning the instru¬ments, interpreting the indications to understand what the airplane is doing and applying the proper control to make the airplane do what we want.
There are two basic attitude instrument flying techniques taught today. One is endorsed by the FAA, the other by the military. Both methods adress the same task, they are both adequate for flight under IFR. However, one technique is ea¬sier to understand.
The military approach to basic attitude instrument flying is much easier to understand and to apply than the FAA techni¬que.The instruments are divided into two categories-control and performance. Performance in¬struments tell us whether the airplane is doing what we want. If not, the con¬trol instruments are used to make necessary changes. These un¬changing categories simplify the task of understanding your instru¬ments during IFR flight.
The control instruments are the attitude indicator and tachome¬ter (manifold pressure for a con¬stant speed propellor). Alti¬meter and VSI measure up and down performance, the directi¬onal gyro and turn coordinator measure directional performan¬ce and the airspeed indicator serves as a cross-check on both pitch and power.
Let's take the case of a standard rate, constant altitude turn. The military or control/performance technique star¬ts with the attitude indicator-roll inthe required amount of bank on this instru¬ment for a stand¬ard rate turn. Now scan the turn coordinator to see if we have a standard rate. Scan back to the attitude indicator and make any neces¬sary adjustment. Next check the altimeter to verify constant altitude and scan back to the attitude indicator to make any required pitch changes. Scan the air¬speed indicator and then go to the tachometer and make any re¬quired power adjust¬ments. Ag¬ain, the control instruments are used to make the adjustment (control inputs) and the performance instruments tell us whether the airplane is doing what we want it to do.
The simplicity of the con¬trol/performance technique stems from the understanding that pitch plus power equals performance. For example at a specified pitch angle and po¬wer setting an airplane will climb at a known airspeed and rate of climb. So, using the con¬trol/performance method to initiate a climb, all we do is pitch the nose up to the proper angle, adjust the power to the proper setting and we get the desired climb rate and air¬speed.
The sequence for the instru¬ment scan is another area of debate among instructors. Most teach the use of the atti¬tude indicator as the focal point of the scan, because it gives the most pertinent infor¬mation about what the aircraft is doing. Beyond this agree¬ment, there is much debate. Some in¬structors teach to scan one instrument, recheck the attitude indicator, check the next instru¬ment and re¬check the attitude indicator and so on. The trick is to perform the appropriate cross che¬cks in case one instru¬ment fails. For example, if the directional gyro tells us we are turning but the turn gyro and attitude gyro show indicatons of str¬aight and level flight, then we should seriously ques¬tion wh¬ether the directional gyro is working properly.
With this point in mind, some instructors prefer checking two instruments before returning to the attitude indicator. if we se¬quentially check instruments that give the same information, it's easier to find the discrepan¬cies between them. For exam¬ple, start with the attitude indi¬cator check the altimeter and VSI as a cross-check on pitch and go back to the attitude indi¬cator to make any adjustments. Next look at the airspeed indi¬cator and power (manifold pressure or tachome¬ter), make any necessary power changes and return to the attitude indicator.
As a pilot gains experience, the exact sequence of the scan will evolve and change. Pilots with hundreds of hours of instrument flying experience seem to have the ability to see and interpret the entire instrument panel as a whole without focusing on each instrument. The bottom line is to cross-check properly the instruments and stick with a scan technique that works.
Now that we have a handle on the basics of scan, interpret and control, let's take a look at how this is applied to airplane mana¬gement.There are an infinite number of variables that affect airplane performance. As long as these are allowed to change,flying is very complica¬ted and difficult. For example, there are countless different combinations of airspeed and power settings that result in descent. Superimpose on these an infinite number of trim set¬tings and we can make a simple descent a near-impossible task that requires all our attention and focus. But if we choose to limit the variables, we can make aconstant-airspeed, constant-rate descent as simple as a minor power reduction. Considering an entire IFR flight where we climb, fly level, de¬scend and perform precission approaches, we see that this performance of variables could keep us quite busy. The key to overcoming this problem lies in a analysis of our aircraft mana¬gement and eliminating some of the variables.
IFR can be divided into six dif¬ferent performance regimes-or six flight configurations. These include climb, cruising straight and level, cruise descent, flying level at approach speed (as when level at MDA in a holding patern or maneuvering for an approach), precision approach descent and non precision ap¬proach descent. If we can de¬termine the proper attitudes and power settings for each of these six configurations, then the pro¬cess of transition from one to another becomes quite simple. Furthermore, if we apply some logic to airspeed and aircraft configuration used for these six regimes, then we gain an even fuller understanding of the air¬plane and what it is doing.
One important concept to un¬derstand is that the elevator trim affects airspeed. If we ad¬just trim for a certain airspeed in level flight and change the power setting, the airplane will either climb or descend as it tries to maintain the same air¬speed at the new powerset¬ting.This concept can be used to our advantage¬.The fewer speed changes we use, the fe¬wer trim adjustments one needs to make.In fact, it is pos¬sible to complete an entire IFR flight touching the trim only twice.
Let's begin our aircraft mana¬gement analysis with cruise and cruise descent.Cruise is what we do most of the flight. We simply hold altitude and perform standard rate turns as we proceed from point of de¬parture to our destination. 65-75% in cruise will give adequa¬te cool¬ing. In a C172 we can choo¬se 2300 rpm and 100 KI¬AS. These numbers are approximate and will vary with density altitude and weight. Why change speed during des¬cent and not maintain 100 kts.? Just reduce to 2000rpm and we have a 500¬fpm de¬scent.look mom, no han¬ds!
Next, consider the climb.In our light aircraft we perform our climbs at best rate. So let's choo¬se 80kts. with full throttle and 10 pitch nose up. The approach phase of a flight is a period of high work load for the pilot and easing that workload figures prominently in the selection of a common air¬speed for all the approach configurations. 80 kts. can be a good choice for the C172. Re¬alize that one of the most criti¬cal phases in a flight can be the transition from an approach descent to missed approach. We suddenly find¬ that we aren't going to land and must divert our attention to a missed approach procedu¬re. This can be a hectic period and anything we can do to re¬duce our workload to a minimum is wel¬comed. So, commom speed and flap set¬ting for the approach descents as we do for the climb-80kts., flaps up. If we do this then all there is to transition to the missed approach is to push the the throttle full
forward. No retrimming, no moving the flaps-just push the thr¬ottle in and go. Eighty knots is also within the flaps opera¬ting range, making it easy to chop the power, add flaps and land the airplane if the approach does work for us.
Choosing 80 kts. as the appro¬ach speed also makes sense from the point of view that an indicated airspeed of 80 kts. in many conditions of altitude and temperature corresponds to a true airspeed of ap¬proximately 90 kts.-one of the approach speeds listed on the approach plates.this makes calculating our missed approach timing a trivial matter.
To prepare yourself for effecti¬vely managing your airplane, put together a table and per¬form an analysis for your aircraft under various flight conditions. Fly your aircraft under VFR on a smo¬oth day, determine the proper power settings and con¬figuration and then record the information on the table. These power settings will only be ap¬proximate figures and will vary. But they are usually within 100 rpm and you can make minor adjustments.Of course the po¬wer setting for the precission approach will be a starting point for no wind conditions and slight corrections will have to be maintained to stay on the glide slope.
Whether you fly IFR or VFR, your ability to control the air¬plane smoothly and focus on other aspe¬cts of the flight will impro¬ve greatly as you learn to effi¬ciently manage the aircraft. The overal result is a safer more relaxing experience in the cock¬pit.
