Safety and ops info

Safety and ops info

Here we offer some unofficial – but hopefully useful – advice about our region’s aerodromes and local airspace, plus general stuff that might not appear in AIP Vol 4, or Notams.

The club takes no responsibility for the accuracy of this information. Local aviators will let us know of local issues, and then we’ll post the information here.

If in any doubt, double-check it.

 

Using the radio: Here’s a happy ending

By Trevor Doig

Most pilots will have at some time, while in general frequency areas, been uncertain from an aircraft’s radio call whether that call represents traffic pertinent to your own movements and intentions. For example, on 119.1 there are many aerodromes and training areas using the frequency, with mainly irrelevant information, so when one call does come through that might be relevant, but you are not sure, alarms ring.

For example, you might be planning to join an airfield and you hear someone else is “five to the west, 2000 feet tracking to join. But is it at the same airfield? Has that happened to you?

Because you missed a very important word. The location of the aircraft.

There is one main reason for this. The human brain takes a moment to identify incoming sound, it has to decide many factors, male, female, urgency, familiarity, language and many other factors. During this process, attention is diverted from the actual message so it is quite usual for the brain not to properly process the first word.

But there are other reasons that exacerbate the problem. Some speak too fast, some pilots in a hurry to transmit are slow pushing the PTT button and the first word is skipped. Perhaps there’s a bit of static. Sometimes the listening pilot is distracted by the many tasks he has to perform and doesn’t focus on the call until it is under way.

This all makes it difficult to distinguish relevant aircraft activity in your area. When you are on the downwind leg at one aerodrome, an incoming circuit call can cause a quick heart flutter and sky search when you didn’t quite catch the first word, but then checking the plate for the runway direction shows the aircraft is at another airfield, and you can relax again. That is not the time to be checking plates and charts and worrying about irrelevant radio calls.

All this can be avoided adopting the practice of repeating the aerodrome name at the end of the transmission. For example, “Dannevirke traffic, XYZ downwind 25 full stop, Dannevirke Traffic”.

Or “Waipukarau Traffic, ZYZ is five to the west tracking North, Waipukarau traffic”.

It is only two additional words but can avoid a huge amount of stress for other aviators.

Why doesn’t everyone do it?

Turbulence and how to avoid the worst of it

What is turbulence? At the levels we fly, most of the turbulence we encounter is one or more of three types:

Mechanical – which is caused when air near the surface flows over obstructions such as hills, mountains, bluffs or even buildings, and is transformed into a complicated pattern of eddies and other irregular movements, or;

Thermal which is caused by uneven heating from the ground due to surfaces being different in colour or in shadow, resulting in air rising at different rates (ever flown over a brown cornfield or ploughed paddock on a hot day?) or;

Unstable air – This is caused by warm surface air rising and, being surrounded by cooler air, it continues to rise. When the air reaches its saturation point, cloud will form. And the warmer air continues to rise.

When an aircraft encounters turbulence, it reacts to the air movements, and especially the wings react to air striking them at different angles. We feel this as bouncing around.

Pilots must be aware of the importance of reducing speed to or below the maximum turbulence speed recommended for the aircraft type when encountering turbulent conditions.

The reason for this is that, at or below the max turbulence speed, the wing will momentarily stall before the design load factor is exceeded. This speed reduces with a reduction in weight. Some flight manuals only give this speed at MAUW, and some give the speed at MAUW and at a reduced weight as well. It is a good idea to know your aircraft’s turbulence speed.

The use of flaps should be avoided, as they reduce lateral control and the max flap speed now becomes your Vne.

Avoiding turbulence

It may be that on a particular day, the best avoidance is to stay on the ground or fly early morning or evening.

A good knowledge of the weather forecast for the intended route and local knowledge is always helpful and could give clues as to where to fly. Do not hesitate to ask someone with experience for advice.

As air flows over and around hills and mountains, the turbulence will be found downwind, the strongest being close to the hills (rotor). Be aware that the conditions can change considerably, with even a minor change in wind speed and/or direction.

It is for this reason that pilots should not assume they will or will not encounter turbulence in the same place every time you are flying, even in similar conditions.

There are a couple of things a pilot can do to avoid the worst turbulence. One is to fly at least 2000ft above the height of the hills or mountains.

Downwind may put you in the wave at this level and is usually smooth, but can have up and downdrafts up to 1000 to 1500 feet per minute.

If you are tracking parallel to the mountains well above the crest, it is possible to find an area that is smooth or a slight updraft by moving slightly closer or further out from the crest. As little as 100 metres either way quite often makes all the difference. The right place can be found with a bit of trial and error.

If the cloud will not allow you to get sufficiently high above the crest, then another alternative is to track as far downwind from the mountains or hills as practicable (several miles) to avoid the worst turbulence which is near to the leeside, and then fly on the windward side of any hills that are there.

In this position, the turbulence will be less, and the general airflow will be rising to flow over the hill. You need to be at reasonably low level to do this (500 to 1000ft AGL).

The above is assuming that you are tracking parallel to the mountains, e.g. HS-MS or similar.

When crossing mountains, it is important to cross at near right angles, as this reduces the risk of rolling in the rotor on the lee side.

Much more care is required crossing ranges from windward to lee, than lee to windward, due the difference in ground speed and the far greater turning radius if you need to turn back – and you may encounter a downdraft just on the lee side, which could force you below the crest if you are reasonably low level. The answer is to cross as high as practicable above the crest, and close to right angles.

A point to consider is that any cloud base is usually lower on the windward side of the mountains than the lee.

Finally, unstable air causes convective clouds such as towering CU and CB to form. There can be a lot going on in and under these clouds, such as up- and down-drafts and erratic air flows, so the answer is simple: do not fly under them, fly around them.

Also, remember that, as non-commercial pilots, there should be no reason to fly in turbulent weather, and nobody should “have to go flying”.

Facts about ‘rough air manoeuvring speed’

In summer months, with turbulence from strong thermal activity, airspeed can be critical and pilot use of controls even more important.

By Steve Walker in KiwiFlyer

A few years ago, I was amazed to read the accident report of an American Airlines A320 which lost its tail and crashed in New York after the co-pilot used excessive alternate rudder inputs when the aircraft encountered wake turbulence from a 747 it was following. The A320 was flying in the green arc on the ASI, still in climb and is one of the most reliable aircraft ever designed, with safeguards designed to protect against pilot error. In this accident, they were flying within the design Rough Air Manoeuvring speed.

That got me to thinking that if such massive structural damage can occur to a new airliner, what about our General Aviation aircraft? Are we right in what we teach student pilots? What effects will manoeuvres such as wing-drop stalls, maximum rate turns, and side-slipping have on the aircraft structure if performed in bumpy conditions?

I then began to think especially about the effects on the airframe when flying in strong turbulence, because that’s when I have experienced the worst conditions. We were taught that, when flying in the green arc of the ASI, we can use full deflection of our controls without damaging the aircraft. As long as the needle isn’t in the yellow arc, we feel safe – no matter how hard the turbulence feels.

How wrong we are.

We are also taught to study the Flight Manual of an aircraft when getting a type rating and we are taught that the Va – Design Manoeuvring Speed – “is the maximum speed at which the limit load can be imposed (either by gusts or full deflection of the control surfaces) without causing structural damage”.

As it turns out, when flying in turbulent conditions (and in New Zealand we frequently experience severe turbulence in strong westerly conditions in the lee of hills or mountains, or in summer under strong cumulus clouds), we can induce severe damage to the aircraft structure when flying at the top end of the green arc.

The certification regulations do not require an aircraft design to withstand a full deflection of a control surface in one direction followed by a full deflection in another even when operating below Va, which is meant to be the maximum speed at which the pilot can make abrupt and extreme control movements and not overstress the aeroplane’s structure.

In designing an aircraft, the regulations don’t require it to withstand the forces caused when two or more control surfaces are simultaneously moved to their stops. Recent studies have shown that such control movements will create G forces that can overstress the aircraft.

The latest definition which changes our entire understanding from what we were taught is “The Design Manoeuvring Speed (Va) is the speed below which you can move a single flight control, one time, to its full deflection, for one axis of airplane rotation only (pitch, roll or yaw), in smooth air, without risk of damage to the airplane.”

Unfortunately many flight manuals do not publish a ‘Turbulence penetration speed’ so we either need to calculate it or use a simple rule of thumb to estimate a speed which should give a pilot enough of a margin over stall speed to be comfortable, and if a gust does cause a sudden stall, the wing at these speeds will recover and no damage will result.

A quick rule is to use 1.7 times the published Vs (stall speed) for the weight of the aircraft during that flight. As fuel is burnt during the flight, the aircraft’s weight will decrease, and as weight changes the stall speed it must be taken into account. The Va or Design Manoeuvring Speed is calculated by multiplying the stall speed by the square root of the maximum load factor. However, you can calculate a new Design Manoeuvring Speed and it is a matter of simple maths using the formula: (Va-New = Va ? (WNew/WMax-Gross).

A large proportion of our privately owned GA fleet in New Zealand is either 15-30-year-old aircraft or relatively new LSA or Advanced Microlights.

All owners need to appreciate the following. The older GA aircraft may suffer from corrosion or other aging processes which can make it more susceptible to structural damage in severe turbulence or excessive G force manoeuvres. Many of the newer LSA and Advanced Microlights are built to European weight limitations of 450kgs MTOW and regardless of whether it’s in the LSA or Microlight category, the aircraft are practically identical.

Even though New Zealand regulations specify a MAUW of 600kgs for LSA aircraft, they are still designed to meet the 450kg limitation to meet the European regulations. These aircraft are designed and built to be as light as possible and owner/pilots need to understand this and fly their aircraft accordingly. In the same vein, any aerobatic manoeuvres – including stall turns, chandelles and lazy eights – should be totally avoided as the pull-out at the bottom of the manoeuvre can overstress the aircraft.

Many of us have experienced severe turbulence and noted the aircraft air speed indicator needle and the vario jumping all over the dials. These are the times we need to slow down and coach the aircraft through the conditions. As the aircraft ascends in turbulence or a thermal, the airspeed will jump rapidly, requiring an immediate reduction in power; the contrary applies in descending air, when sometimes full power is required to arrest the descent.

I’ve seen a few cockpit canopies cracked and broken when struck by the pilot’s head so even tight harnesses don’t always hold the pilot in place. For those of us living and flying in hilly or mountainous areas of the country (and that makes up most of New Zealand) the conditions I depict are normal flying conditions we experience except on those rare calm days in winter.

Our flight training manuals and student hand-outs need to now be modified to clarify the “Rough Air Manoeuvring Speed” to read “The Design Manoeuvring Speed (Va) or Rough Air Manoeuvring Speed is the speed below which you can move a single flight control, one time, to its full deflection, for one axis of airplane rotation only (pitch, roll or yaw), in smooth air, without risk of damage to the airplane.”

It is very clear that if the pilot were to deflect the ailerons and elevator at the same time, added by a kick on the rudders to avoid an in-flight upset in strong turbulence, there is a strong chance the aircraft will be bent.

I’ve always hated getting bounced around, and have always reduced speed to just above Vfe (flap extension speed) in strong to severe turbulence, and it takes considerable use of the throttle to control the airspeed. It’s a much more comfortable ride and I know my aircraft isn’t suffering.

 

Pilots, know your Vs

by Ken McKee

It was one of those typical sunny Hawke’s Bay days and Fred decided to fly to Feilding and visit friends there.  He took his pilot friend Joe and they had a nice flight to Feilding.

Later that day when returning to their home base in Napier, Fred noted that the westerly wind had picked up and said to Joe: “Better tighten your harness, it could get a bit rough”.   As they got in the lee of Wharite Peak, they encountered severe turbulence and Fred needed to use maximum aileron to maintain level flight.  For the comfort of those on board, Fred immediately reduced the normal cruising speed of 90 knots even though the top of the green arc was 95 knots.  Should Fred have been thinking of anything else?

Aircraft have many operating limitations that can be found in the Flight Manual.

One of these is expressed in terms of airspeed or velocity (V).

Pilots need to be familiar with the airspeed limitations of the aircraft they are flying.  The following is a simple explanation for a complex subject and applies to single-engine fixed undercarriage aircraft.

If the limiting airspeeds are exceeded, the aircraft will suffer structural damage.

If the limiting airspeeds are exceeded and the aircraft is at the same time subjected to added ‘G’ forces, the aircraft could suffer catastrophic structural failure.

The following are the most important limiting airspeeds:

  1. Vne or Never Exceed.
  2. Vno or Maximum structural cruising.
  3. Va or Maximum Manoeuvring.
  4. Vfe or Maximum Flap Extended.
  5. Vs or Stall.

Vne is marked on the airspeed indicator (ASI, Fig 1) with a red line. This speed must only be approached in calm air and must not be exceeded under any circumstances.

Vno is marked on the ASI as the upper limit of the green arc. This speed is the maximum normal operating speed and at which only normal, gentle flight control movements are permitted.

Va should be placarded, ideally adjacent to the ASI.  It is also known as the maximum rough air speed.  This is the maximum speed at which one of the flight controls can be moved abruptly and/or to its maximum deflection in one direction.

Note that moving the flight controls abruptly from maximum in one direction to maximum in the other direction can cause structural failure at less than Va.  Va is calculated by multiplying the square root of the positive limit loASIad factor (G) by the clean stall speed (Vsi), at MTOW.

Vfe is marked on the ASI as the upper limit of the white arc.  This is the maximum speed at which the flaps can be extended.

Vs is marked on the ASI as the lower limit of the green arc.  It is the airspeed at which the aircraft will stall with no additional ‘G’ forces applied.

On the airspeed indicator, the flap speeds are in the WHITE arc, the normal operating speeds are in the GREEN arc and the caution airspeeds are in the YELLOW arc.

When the flaps are extended, the airspeed must be in the white arc.  Flying in the green arc should be safe in all normal flying conditions.  When flying in turbulent or rough air, the airspeed should be less than Va.  Flying in the yellow arc requires caution and is only permitted in smooth air.

Remember, the elevator controls the airspeed.  In order to reduce airspeed when suddenly encountering rough air and the airspeed is above Va, it is sometimes necessary to not only reduce power but also to gently raise the nose attitude.

If at any time you think you may have overstressed an aircraft, speak with a qualified person and if necessary have the airframe inspected by an IA before it is flown again.

By the way, the Va of Fred’s aircraft is 83 knots.

 

Non-standard turns at Hastings

Visitors and club members need to be aware that making a “non-standard turn” when vacating from the Hastings airfield to the east from either 01 or 19 is not permitted.

Another aircraft could be joining from the east into the crosswind. The bang could be significant.

All turns in the circuit are to be made in the circuit direction.

Gliders frequently operate at Hastings and they use the “non-traffic” area with a right-hand circuit. Either avoid this area or exercise caution within it.

 

Operations and Safety Guide

The club’s Operations and Safety Guide is located here and there is a link to a downloadable, print-ready copy in PDF format. There are also links to CAA and RAANZ websites, to access copies of their various report forms.

The document will be amended from time to time, so please pay the occasional visit to the Guide page and check the Updated date for the latest version.

 

Waipukurau

The southern end of Waipuk’s runway can become soft after prolonged rain. Soft areas will be indicated by cones directing you to the displaced threshold. Expect to find a healthy layer of Central Hawke’s Bay sheepshit on your aircraft after a successful landing, when the flock of cost-reducing sheep are mowing the grass. It’s a small price to pay for not paying a landing fee. Ample supplies of soap and water are available, and Ross Macdonald can be relied on to help you scrub your aeroplane back to near-new condition.

Hastings

When on finals for runway 19 in a strong westerly, be aware of the line of trees bordering the threshold on your right, and aim to land late. Or make use of runway 29 (remember to call it). Watch out for the displaced threshold on runway 11. It’s there because of power lines on the approach.

When joining overhead, which is not advised unless you are fully aware of the traffic, you might meet a transient glider or sight our unpleasant Regional Prison just east of the airfield. Overhead joins are not recommended – check the aerodrome’s AIP plate. Straight-ahead departures from 01 will put you in Napier controlled airspace, and right turns after a 01 departure may get you into trouble.

Nordo aircraft are based on the field.

Omaka

From Alistair Matthews and the team at the Marlborough Aero Club: please take note when flying into the Omaka Airfield.

A couple of incidents on the airfield have highlighted a threat to our safety which has always been there and will be there for all of us to continue to manage and reduce by appropriate action.

I am talking of the thresholds of runway 01 and 07 which cannot be seen from each other because of the vineyard between. We have had two close calls in quick succession; no pilot was doing anything wrong, but we need to raise awareness.

How can we reduce this threat? Start at the beginning, when you start to taxi for either (or any) runway. Make your taxi call and listen out for any replies or calls from other aircraft. Look around as you taxi for aircraft on the ground or in the sky. Get that situational awareness going, note who is doing what. We know that the wind can often be between 01 and 07 so one pilot thinks it favours one but another pilot thinks it favours the other. Neither is wrong and it is perfectly OK to take a runway with a crosswind, but you must be sharp as to what is happening on the other runway.
Convention has us using the same runway others are using, if possible. But it may not be: 01 is longer and may be required by some for performance issues.

Prior to lining up, a radio call and a good lookout, all around, pause for a moment to check on what is happening. Another fish hook: aircraft do not require a radio to land at Omaka so do not rely on that, however use it if you have it. The Mk 1 Eyeball is the big thing, but you cannot see through a vineyard!

If you heard or saw an aircraft on your taxi out, ascertain where it is prior to lining up, spot it, or call up “Aircraft joining Omaka, your position please”. Don’t roll until you know where it is.

Another threat is that looking from 07 to 01 finals, aircraft can blend into the hillside; check carefully.

Raglan

This is a pilot’s paradise, with the motor camp less than 50 metres from the strip and the buzzing village centre a short walk away. But there are traps for the unwary on approach to runway 23. As the customary sea breeze wafts over trees to the starboard just beyond the threshold, wind-shear is often created – leading to a sudden loss of lift and airspeed. Be prepared, and land late if need be.

How to find a harp in a cloud

If you have ever been tempted to just nip inside that little cloud and see what a wrestler’s armpit really looks like, here’s a simple tip. Don’t. Many a World War II fighter pilot died trying it. For microlight pilots, it’s illegal.

Forget your flash EFIS display with its artificial horizon. It’s just there for showing off to people on the ground – or perhaps monitoring a correct turn or climb, if you seek great accuracy.

Unless you have several dozen hours of instrument flight training and the instrument scan is now second nature, you will lose all your senses within 30 seconds. Death or serious injury is the most predictable result.

Here’s a cautionary tale from a microlight pilot who, suffering from an attack of Pressonitis (also known in New Zealand by the less elegant term of get-there-itis), was lucky to survive a moment of sheer folly:

http://www.bmaa.org/news_item.php?wnID=5108

Cross-control stalls

It’s strange but true: the only group of pilots who are tested on cross-control stalls are CFIs. Yet this is the stall that often causes the low-altitude stall spin accident. A cross-control stall occurs while in a skidding turn caused by excessive bottom rudder. By bottom rudder, we mean that if we are turning right, the bottom rudder is the right rudder.

In this situation, the low wing – which is effectively being slowed down by the excessive bottom rudder, will stall before the top wing – which is being accelerated by the excessive bottom rudder. When this happens, the aircraft rotates to the right and the nose drops.

The natural reaction is to pull back on the yoke and apply left aileron, both of which are incorrect. If you do this, the aircraft will continue to rotate and it will enter deeper into the stall. The correct reaction is to apply forward elevator and opposite rudder. Of course, the real solution is to not create a cross-control stall.

You can initiate a cross-control stall from a slipping turn as well, but this is not so dangerous. When we stall in a slipping turn (that is, with excessive top rudder), the top wing stalls first and effectively levels the wings. This presents a much more normal picture to the pilot and almost acts as an automatic recovery.

The Airplane Flying Handbook describes the cross-control stall as a stall from a skidding turn because it requires proper technique to recover and, if not performed correctly, can result in a spin.

This edited article comes from http://www.pilotworkshop.com/tips/cross_control_stalls.htm

The comments beneath the article are also of interest.

To which we also add:

A side-slipping descent, unless unusual circumstances apply, sometimes indicates a poorly constructed approach.

 

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