low level navigation
Writing an article for our training notes on Low Level Navigation. would be very keen for any inputs or suggestions. cheers .
Low level navigation, often referred to as scud running, is a procedure that can be fraught with hazards. It must me pointed out that low level navigation is a technique used in marginal VMC. By marginal VMC, I stress that it is still VMC. The pilot should never allow himself to fly into non VMC conditions. This could well lead to disorientation or failure to see and avoid obstacles Low level navigation should only be conducted after careful consideration to ensure that the legal requirements can be met. The purpose of the chapter is not to encourage you to undertake low level flying but rather to practice it in the training environment with your instructor, in the event that you do ever need to do it.
Let’s use this opportunity to cover what is meant by VMC in each of the airspace categories.
In Class C airspace- Visibility of 5000 metres.
1500 metres horizontal separation from cloud.
1000 foot vertical separation from cloud.
In Class D airspace- As with Class C airspace.
In Class E airspace- As with Class C airspace.
In a GAAP- Visibility of 5000 metres.
Clear of cloud.
In Class G airspace- generally the same as class C Airspace
The exception being if we are below 3000 ft AMSL or 1000feet AGL ( whichever is the higher ) when the visibility remains unchanged at 5000 feet but we can operate clear of cloud and must remain in sight of ground or water.
Pilots are also reminded of CAR 157 with regard to low flying which basically limits flight over populated areas to 1000ft agl and 500 ft agl over non populated areas.
The reason that pilots get themselves into flight in non VMC conditions is generall an overestimation of their ability and an overly optimistic assessment of the weather conditions ahead.
Generally a turn back through 180 degrees will be the best option. Why don’t pilots do this? One reason could be the illusion that the conditions behind you are deteriorating quicker than they really are. This is because at the speeds that aircraft fly at, reference points disappear behind you in the restricted visibility. Ahead of you, as more terrain comes into view there can be the illusion of improving conditions. The faster the aircraft, the stronger this illusion. Conditions don’t usually deteriorate that quickly. If the weather conditions behind you were acceptable 3 minutes ago then the chances are that they are still acceptable
Features such as highways and roads make good features to follow. Keep these features on your left hand side wherever possible. This will make your operation substantially safer. This is where your field of view will be greatest sitting in the left hand seat. Also bear in mind that as the cloud base is lower than normal all traffic will be compressed down into the area that you are flying in, and generally not flying at the standard cruising levels. Hopefully on coming aircraft will also be keeping these features on their left hand side and therefore reducing the risk of a head on collision.
Prior to conducting low level navigation the aircraft needs to be configured.
Another aid in reducing the risk of a head on collision is to maximize the aircraft lighting. Turn on all aircraft exterior lighting.
VHF communications will be reduced at low level and you should expect a reduced range of any navaids. Consider notifying ATC of your intentions.
Ensure that the fuel tank is selected to the fullest tank in the Piper aircraft and selected to both if flying the Cessna aircraft. Ensure you are maintaining a fuel log.
Check all switches and maximize use of any exterior aircraft lighting. With a low cloud base and low flight the risk of a mid air collision is potentially increased as any traffic is condensed down into a lower vertical spread of available airspace with aircraft not being able to fly at the correct cruising levels.
Trim the aircraft for a slight nose up attitude. This is to help protect against a lapse in concentration having the aircraft have fly down towards the terrain.
It is important to keep your eyes outside the cockpit as much as possible. Have your maps correctly folded for the applicable area and keep the map between your thumb and control column to minimize the need to look down at a map on your lap.
Visually separate yourself from terrain rather than relying on the altimeter. Have a good appreciation of what 500 feet agl looks like.
If flying through a valley wherever practical keep to the downwind side of the valley. If a turn through 180 degrees does become necessary the turn into wind will reduce the radius. Bear in mind that a turn at slow speed with a steeper bank angle will offer the best turn performance. Not forgetting of course that your stall speed will however be increasing. Limit bank angle to no more than 30 degrees and increase power during the turns to increase the margin above the stall speed. Flying downwind will also help to reduce the effects of mechanical turbulence.
Flap slow the aircraft and improve forward visibility. At 120 knots 5000 metres visibility is less than 1 and a half minutes ahead. By slowing the aircraft down to 80 knots you will be able to see slightly over two minutes ahead. Still not great but substantially better.
With regard to the navigation technique there are a number of factors that must be considered.
Vertical features will become more important for navigation. Features such as buildings towers, low level hills etc will become easier to pick up than at higher levels but will move quickly past your field of view.
You will have a greater impression of speed at low level so you may think you are going faster than you really are. Aim for slow enough to avoid obstacles but keep a safe margin above the stall speed
Engine failures although unlikely must be considered. Maintain a good situational awareness and treat an engine failure as an engine failure after takeoff. Know the wind direction and have a plan for an engine failure.
Don’t pass up the opportunity to pull into an airport or conduct a prec search and landing over a suitable field. Much better to be on the ground wishing you were in the air than in the air wishing you were on the ground.
Whilst the VFR pilot should not be in IMC conditions if it really does become unavoidable consider a gentle climbing turn in the area to at least have better terrain avoidance. Don’t be afraid to ask for help. Although you as the pilot in command are responsible for your flight I have heard ATC provide wonderful guidance and assistance to a pilot under a stressful situation. A problem shared is a problem halved.