FLYING ON INSTRUMENTS

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Peter Armstrong
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Re: FLYING ON INSTRUMENTS

Post by Peter Armstrong » Mon Jun 24, 2019 6:14 am

The Night Circuit (Pattern)

The circuit pattern at night is usually the same as that by day, except that it is flown mainly by instruments, with reference to the aerodrome lighting to assist in positioning the aeroplane suitably. The normal techniques of attitude flying apply. There is often a tendency to overbank at night, so special attention should be paid to bank angle.

Once the aeroplane makes the first turn, the runway and aerodrome lights will be easily seen and should be referred to frequently. Well-lit landmarks may also be useful for positioning in the circuit.

Allow for drift on the crosswind leg, and level off using normal instrument procedures. Maintain height accurately and carefully scan outside before making any turn. A good lookout for other aircraft must be maintained at all times, and the usual radio procedures followed. Recognising the navigation lights of other aircraft, and responding with an appropriate heading change, will avoid collisions. Example: - While green to red is not safe, this will be the situation with two aeroplanes flying parallel on downwind. An especially careful lookout will need to be maintained.

Listening to radio transmissions will help you maintain a picture of what else is happening in the circuit.
The turn from downwind onto base leg should be made at the normal position, with reference to the runway lights and any approach lighting. The descent on base leg should be planned so that the turn onto final commences at about 600 – 700 ft aal, ideally with a 20 deg bank angle, and certainly no more than 30 degs,
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Re: FLYING ON INSTRUMENTS

Post by Peter Armstrong » Tue Jul 02, 2019 12:22 am

The Night Approach

A powered approach is preferable at night, rather than a glide approach. In modern training aircraft, the powered approach is generally used by day also. Power gives you more control, a lower rate of descent and, therefore, a less steep slope. The approach to the aiming point should be stable, using any available aids, such as the runway lighting and a PAPI (precision approach path indicator) if available.

Using the runway edge lighting only, correct tracking and slope is achieved when the runway perspective is the same as in daylight. For correct tracking, the runway should appear symmetrical in the windscreen. Guidance on achieving the correct approach slope is obtained from the apparent spacing between the runway edge lights. If the aeroplane is getting low on slope, the runway lights will appear to be closer together. If the aeroplane is flying above slope, then the runway lights will appear to be further apart. Also pay attention to the ASI throughout the approach, to ensure that the correct airspeed is being maintained.
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Re: FLYING ON INSTRUMENTS

Post by Peter Armstrong » Mon Jul 08, 2019 1:20 am

The Night Approach – continued

If no PAPI is available, the aiming point during the approach should be a point somewhere between two and four runway edge lights along the runway from the approach threshold.

If there is a PAPI available, the aiming point during the approach should be the PAPI. Because it is an approach aid and not a landing aid, the PAPI should be disregarded once below about 200 ft above aerodrome level, and attention placed on the perspective of the runway edge lighting in anticipation of the flare. Following the landing flare and hold-off, the aeroplane will of course touch down some distance beyond the aiming point used during the approach.

Any tendency to drift off the extended centreline can be counteracted with coordinated turns, and drift can be laid off if a crosswind exists. Be prepared for wind changes as the descent progresses – the difference between the wind at 1000 ft aal and at ground level is likely to be more pronounced at night than by day. It is common for the wind speed to decrease and the wind direction to back as the aeroplane descends.
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Re: FLYING ON INSTRUMENTS

Post by Peter Armstrong » Thu Jul 11, 2019 8:44 am

The Night Approach – continued

Any variations in slope should be corrected with coordinated use of power and attitude. The aiming point should stay, on average, in the same position in the windscreen. Stay on airspeed during the approach. Check airspeed on the ASI, and do not be afraid to use power. Occasionally check the altitude.

Once approaching the threshold, the runway lights near the threshold should start moving down the windscreen, and certain runway features may become visible in the landing lights. The PASPI guidance will become less valuable below about 200 ft and should not be used in the latter stages of the approach, and certainly not in the flare and landing. The PAPI is an approach guide only. It is pilot judgement that counts in the landing.
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Re: FLYING ON INSTRUMENTS

Post by Peter Armstrong » Wed Jul 17, 2019 2:02 am

The Flare, Hold-off and Landing at Night

The aeroplane should be flown on slope towards the aiming point, where the landing flare will occur. The best guide to flare height and round-out is the runway perspective given by the runway edge lighting. As the aeroplane descends towards the runway, the runway edge lighting that you see in your peripheral vision will appear to rise. The appearance of the ground can sometimes be deceptive at night so, even when using landing lights, use the runway lighting as your main guide in the flare and hold-off, both for depth perception and for tracking guidance. For this reason, your introductory landings may be made without the use of landing lights. When you are using landing lights, do not stare straight down the beam, but to one side.
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Re: FLYING ON INSTRUMENTS

Post by Peter Armstrong » Tue Jul 30, 2019 2:41 am

The Flare, Hold-off and Landing at Night (continued)

There is a common tendency to flare and hold off a little too high in the first few landings at night, but this tendency can soon be modified with a little practice. The runway perspective on touchdown should resemble that on lift-off, and an appreciation of this is best achieved by looking well ahead towards the far end of the runway. Avoid trying to see the runway under the nose of the aeroplane. This will almost certainly induce a tendency to fly into the ground before rounding out.

As the aeroplane is flared for landing, the power should be gradually reduced as the aeroplane enters the hold-off phase, and the throttle fully closed as the aeroplane settles onto the ground during touchdown. Keep straight during the landing ground run with rudder and, in any crosswind, keep the wings level with aileron.

Keep on the centreline until the aeroplane has slowed to taxiing speed, using brake if necessary. Taxi clear of the runway, stop the aeroplane, set the brakes to PARK, and complete the after-landing checks.
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Chris Brettrager
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Re: FLYING ON INSTRUMENTS

Post by Chris Brettrager » Tue Jul 30, 2019 11:38 pm

Peter Armstrong wrote:
Tue Jul 30, 2019 2:41 am
The Flare, Hold-off and Landing at Night (continued)

using brake if necessary
If necessary, suggestions of times it isn't necessary to use brakes on landing haha
The Don - I've been here for too long...
"He who stands a top the mountain for everyone to see, does not lead. He who finds a way to move the mountain, he is the one who leads." - Christian Brettrager

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Re: FLYING ON INSTRUMENTS

Post by Peter Armstrong » Wed Jul 31, 2019 2:43 am

The go-Around at night

The flying technique for a go-around at night is the same as by day, except that it is done primarily by reference to instruments.

Whereas the eyes may be concentrated on the runway lighting during the latter stages of the approach, these lights are no longer necessary when full power is applied and the pitch attitude is raised. There will be strong pitch and yaw tendencies due to the power increase that must be controlled with reference to the flight instruments. Hold the desired attitude on the AI, monitor vertical performance on the altimeter, monitor airspeed on the ASI, and hold direction on the DI.

Do not change configuration (flaps/gear) until established in the go-around, with a positive rate of climb indicated on both the altimeter and the VSI.
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Re: FLYING ON INSTRUMENTS

Post by Peter Armstrong » Wed Aug 07, 2019 2:52 am

Wind Variations with Height

The surface wind at night may differ significantly from the wind at height. The term surface wind refers to the wind measured 10 meters (30 feet) above open and level ground – where windsocks and other wind indicators are generally placed. The surface wind is generally weaker than the wind at altitude because of the friction forces existing between the lower layers of the airflow and the earth’s surface, which slow it down. The rougher the surface, the greater the slowing down effect. The wind well away from the influence of the surface, typically some thousands of feet above it by day and possibly only 500 feet above it at night, is known as the gradient wind.
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Re: FLYING ON INSTRUMENTS

Post by Peter Armstrong » Mon Aug 26, 2019 5:12 am

Wind Variations with Height…. continued

There will be some vertical mixing in the air mass near the earth’s surface, depending on a number of things, including heating, which will cause thermal eddies in the lower layers. During a typical day, the earth’s surface is heated by the sun. The earth’s surface, in turn, heats the air near it, causing the air to rise in turbulent eddies and mix with the upper air. This vertical mixing in the lower levels of the atmosphere brings the effect of the gradient wind closer to the earth’s surface.

With vigorous heating (such as over land on a sunny day), the friction layer is deep, and so the stronger upper winds are brought down to lower levels; if the thermal eddying is weak (such as by night or over a cool sea), then the vertical mixing is less, and the friction layer shallower……….to be continued
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Re: FLYING ON INSTRUMENTS

Post by Peter Armstrong » Fri Aug 30, 2019 12:39 am

Wind variations with height

At night therefore, with less heating and less mixing, the effect of a strong gradient wind will not be brought as close to the earth’s surface, resulting in a surface wind that is lighter at night than by day. A light wind of 10 kt by day may fall to become practically calm by night, even though the upper winds have not changed.

A consequence of a reduced wind speed is a reduced Coriolis effect, hence the surface wind will back compared to the wind at altitude, i.e., the wind direction will move anticlockwise as the aeroplane descends. (The effect is opposite in the southern hemisphere.)

The difference in wind strength between the surface and at height will generally be more marked at night and, if there is a sudden transition from the lower winds in the shallow friction layer to the undisturbed upper winds at a particular height, say at about 500 ft, then windshear could be experienced as the aeroplane passes through this level.

A surface wind of 5 kt at take-off may suddenly become 20 kt at some low level on a clear night (possibly with a significant change in direction as well), yet only 10 kt at 1,000 ft on a clear and sunny day.

Notes:
• The wind at altitude is usually stronger than the surface wind
• The surface wind will back compared to the wind at altitude
• Expect stronger and sharper wind changes as you climb out by night
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Re: FLYING ON INSTRUMENTS

Post by Peter Armstrong » Sun Oct 13, 2019 8:09 am

Emergencies at night

Engine Failure

A forced landing at night away from an aerodrome is obviously a more dangerous event than by day, when better vision will allow the easier selection of a suitable field. Moonlight may help at night, but do not count on it! Normal daylight procedures should be followed if the engine fails at night, with the emphasis on keeping the aeroplane at flying speed and restarting the engine.

Flying the aeroplane at a low forward speed consistent with retaining full control will help achieve a lower rate of descent, and allow more time for remedial action and for carrying out a forced landing if necessary. A Mayday call should be made promptly to alert the rescue services.

Time available for action will depend on height above the ground, so reference to the altimeter is important. Make a common sense judgement of your height above the ground, and keep a good lookout. If sufficient height and time is available, glide the aeroplane (at a safe speed) back to the aerodrome, while troubleshooting the problem.
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