Flying is not a natural thing for people to do. We are ground-based creatures with a physiology developed to cope with that environment, not flying through the air in such marvellous machines. This is most applicable to our balance system, it is geared to help prevent us from falling over or from falling off things and it can severely impair our performance when flying particularly at night, in the cloud or with very poor visibility.
Without going through all the physiology that you would have or are about to learn about. Our balance system relies on information from 3 sources
- Our muscles and joints.
- Vestibular organs in the inner ear
- Our eyes.
In an aeroplane, our muscles and joints and our vestibular organs don’t work incredibly well (ergo- they’re rubbish). We can fly at 60 degrees angle of the bank and;
- Our muscles and joints will tell us we are heavy, but not inclined at 60 degrees to the horizon.
- Our vestibular relies upon the movement of fluid, just like the balance ball on the turn coordinator, if we have remained in balance whilst rolling and remain in balance whilst turning- not going to tell us anything. Also, will lie to us if we get out of balance and may confuse pitch with acceleration- a useless piece of kit.
- Our eyes- our knight in shining armour, they will sort out those incorrect messages from our muscular and vestibular wastes of space, however- lose sight of the natural horizon and they too now become as useful as the runway we left behind us at the start of our take-off roll.
The early pioneers of aviation were not aware or sometimes didn’t care about this failing of our system, how could what our bodies feel be wrong? End result, spearing into the ground from a spiral, pitching the nose down further as they felt the acceleration from pitching the nose down and spearing into the ground or a combination of both- sweet dreams and flying machines in pieces on the ground. The solution- invent instruments that give us accurate awareness of the aircraft’s pitch, roll and yaw and train pilots in the use of these instruments, combined with scanning other instruments as a backup, to overcome the deficiencies of us, mere mortals
Another issue also arose- hitting cumulo-granite hurts, and flying into hills or mountains is not good! Solution, fly high enough to avoid them when you can’t see them with a buffer (1000 ft), once below this height, develop instruments and procedures to descend to a safe height where you can see the runway, followed by a “quick” approach and landing- training required for this one also, takes a bit of skill that has to be learnt.
One more issue, if you can’t see them, they can’t see you, hitting another aeroplane will make the news. Solution- use radios and air traffic controllers to separate aircraft or outside controlled airspace, use radios and each other to separate yourselves. With all the other things going on, preventing yourself from losing control plus preventing yourself from hitting the ground, this can be difficult and requires training.
Finally, another issue- getting lost because you can’t see where you are- is pretty well handled by the instruments used to avoid hitting the ground.
All in all, master these tools and you don’t need VMC, you can be unleashed into the world of IMC by flying under the IFR. For those who don’t have a rating, If you have the time and the cash, have a think about doing an Instrument rating PIFR or Command, PIFR is great as it can be tailored to your need and budget. Flying under the IFR (legally) in addition to extending your available flying, really improves all flying skills and discipline and is great fun.
For those not inclined or wanting to fly in good weather without all the “procedural stuff” associated with IFR, back to my subject- VMC.
VMC prevents us from encountering all the nasties mentioned above. The following is an analysis of VMC below 10,000 feet in class G airspace above either 3000 feet altitude or 1000 feet from the ground whichever is higher.
- Visibility (5000 metres or greater) – This will prevent any issues with the balance system, will allow you to see terrain and will assist with sighting other aircraft. It’s not that much, 5 km = 2.7 nautical miles, 1.5 minutes in a C172.
- Cloud (1500 metres, 40 seconds in a C172) horizontally from cloud, (1000 feet vertically). This serves 2 purposes:
- Prevents you from inadvertently entering the cloud and experiencing the nasties mentioned above.
- Gives you time to sight any IFR aircraft that may be skipping through or climbing/descending from the cloud particularly if you don’t have a radio.
Now the reduced VMC criteria when below altitude 3000 or 1000 above ground. Clear of cloud.
When I learnt to fly……
This didn’t exist, however, it was reasonably common that if you were just a little bit closer to the cloud in such conditions, you did it. Fortunately, CASA rectified this and insisted upon one very important criterion- radio must be carried and used on appropriate frequency. IFR aircraft don’t fly in IMC typically below 3000 feet and not below 1000 feet AGL unless conducting an approach. Be listening for that aircraft about to make the approach and communicate with them, some positive action will be required, confirmation or arrangement of separation either laterally, vertically maybe even your landing to let them “get in”, cooperation is required. Please, don’t think that because you have talked to them, everything will be OK. They may be somewhat of a dill, confirm that you will maintain separation.
One more thing on remaining clear of clouds below 1000 feet AGL. Please ensure that you will have no problem maintaining clear of cloud, and make sure that at all times you have an escape option if you begin to lose this option- do something about it. If you are below 1000 feet AGL and you enter the cloud, there is a very high probability that you will pass, you will become deceased, you will fall off the perch, etc. etc.
Finally
Class D airspace, the clear of cloud option for VMC does not exist. To operate under the VFR you must have 5000 metres visibility and you must be 600 metres horizontally from cloud, 500 feet vertically below and 1000 feet vertically above. That is- returning from Forrestdale Lake and a cloud is less than 500 feet vertically above you, you will need to steer 600 metres away from it horizontally, this would be a violation of your clearance. However, help is at hand! If you are confident that you can safely handle the conditions, you can request Special VFR to enter or leave the CTR. This will normally be given by the Tower unless they have IFR aircraft, they can’t allow an aircraft to descend out of IMC and be confronted by bugalugs flying special VFR. They may delay you however if this will create safety concerns for you- speak up.
As a reminder- Special VFR you are responsible for ensuring that:
- The flight can be conducted clear of cloud
- The visibility is not less than 1,600 metres (just under 1/3rd of the CTR)
Remembering 1,600 metres is .9 of a nautical mile, just under 30 seconds in a C172- not very far, so please be cautious.
Until next week. Smooth landings,
John Snare
Safety Manager
Photo by Rafael Cosquiere: https://www.pexels.com/photo/two-pilots-sitting-inside-plane-2064123/
