Navigating

22 February 2022

Things are progressing in my simulated flight school but questions keep popping up – the latest one was “how do I find my way from point A to point B?” It sounds simple but turns out to be not really so.

Naturally, today we have GPS for planes – even if the plane is not fitted with one, you can add it just like you do in a car, program in a route and simply fly the route shown on the GPS. However, to gain a license in the real world you must be able to navigate without one to start with – ‘Visual Flight Rules’ or VFR flying must be mastered first. VFR flight demands that you can find your way using visual references – things like cities, large roads, lakes, large rivers and so on.

I’m practicing VFR flight at the moment and it’s not easy, we can all spot London but could we spot Luton or Kings Lynn from the air if you had not seen them before? This type of navigation in flying is termed ‘Pilotage’.

After some research I found that pilotage is closely connected with dead-reckoning. Dead-reckoning (or ded-reckoning) is the method of working out a route from A to B using charts, headings, speed, time and so-on, it is one of the oldest forms of navigation. This topic peaked my interest so I dived in.

Firstly, it can all be done online now or even using an app on the phone, but where is the fun in that? I needed some toys – a UK VFR chart – this is a map of part of the UK, laminated so you can write on it, it contains a massive amount of information regarding everything needed to plot a route, part of one is shown below.

Next I needed a navigation protractor, these are (generally) square protractors, marked with compass headings, they also have a grid in the centre divided into nautical miles (NM) at the same scale as the VFR chart of 1:500,000, this one has a 4NM grid with subdivided cross-lines.

Next I needed a computer, not a PC, but a manual computer, one side of one is shown below. This is a multi-function slide-rule device. All the work that this device does can be done on a single PC or phone app or web site now but I don’t think that’s as much fun as a slide-rule 🙂

All the data and calculation results are entered on a Pilots VFR Flight Log or ‘PLOG’ sheet, an example is shown below. The PLOG is taken along and referred to on the actual flight, it can be clipped to a pilots kneeboard (a clipboard with a leg strap).

All of my new toys were found on eBay for very little cost – the chart is out of date for real flight but fine for simulated flying, the computer was used as was the protractor. The whole lot cost me about £20 which I think is a pretty good price compared to new which would be around £80 or more. The charts get replaced when radio frequencies change or airfields close etc. – important for real flight but not so much for virtual.

Dead-reckoning navigation seems to be a matter of flying a certain course for a given amount of time at a known speed, along the way you compare notes made on the PLOG regarding visible landmarks to keep checking and verifying your course. Calculating the course requires taking into consideration the weather – wind speeds and direction, temperature, your normal cruising speed, even the variation in the earth’s magnetic field needs compensating for.

It’s a fascinating but complex topic but my experiences will be recorded here for fun…

25 February 2022

Still waiting on some bits of my kit to arrive, I have started research into what the task entails. It’s complex but luckily for me in the virtual world, I can ignore certain parts that will not affect me 🙂

Dead-reckoning overview:-

• 1 – Decide the route from A to B
• 2 – Gather safety notices, warnings & restrictions
• 3 – Plot the route on the map
• 4 – Record the entries on the PLOG that are gathered from raw data
• 5 – Get the weather at the altitude needed
• 6 – Calculate and enter the other PLOG entries
• 7 – Calculate fuel quantity
• 8 – Calculate mass and balance

Point 2 can be ignored for now as I literally have the whole world airspace to fly in so running into military airspace is highly unlikely to matter to me. Point 8 can be largely ignored as my little Cessna 152 is not likely to be loaded with goods and overweight passengers so it will be ok to fly.

The first trial will be a simple straight route from airfield to airfield, probably around 40NM as I know this will take less than an hour to fly and an hour is a long time in a Cessna 🙂 Being in a simulated world, I can set the weather to pretty much any type so I’m hoping to try the route in good weather and then calculate it again with winds from a totally different direction to prove calculation effectiveness etc. I’ll tackle each point as I go…

26 February 2022

All the toys are in, here we go…

1 – Decide the route

My chosen flight is from Stansted airport in Essex (EGSS) to Norwich Airport in Norfolk (EGSX). This is a nice straight route, lots of (hopefully) visual reference points (VRP’s) en-route, both airports are large and easily visible. There are no mountains so my altitude can be kept pretty low to save time in climb and descent stages – the little Cessna 152 is pretty slow and low powered so it takes its time climbing to high altitudes.

2 – Gather safety notices, warnings & restrictions

Stage skipped as not really necessary in a virtual world and at this stage of learning – I can add restricted areas etc later on.

3 – Plot route on map

The route marked on the VFR map, Stansted is at the bottom left and Norwich at top right. The centre point is marked and I have added half-marks for my VRP’s. The first VRP is Haverhill, a fairly large town which should pass on my left, next is Bury St Edmunds, a very large town I should pass right over. Then we have Old Buckenham airfield which should pass just off to the right.

The VRP’s are fairly evenly spaced and hopefully big enough to spot easily, thats the idea anyway 🙂

4 – Record the entries on the PLOG that are gathered from raw data

Here we have the start of the PLOG, I have entered my start and end points plus the VRP’s in between. Next I checked along the route 5NM each side of the planned path for obstacles, these heights were rounded up and 1000′ extra was added, the plan altitude was just a nice figure I chose that was higher than the obstacles.

Then we have TAS or true air speed, this is my chosen cruise speed, the 152 is happy around 90-105 knots. TR(T) is the true track – this is measured off the chart using the square protractor, it is the heading of the line compared to true north, as my line is straight there is only one value and all legs are the same.

5 – Get the weather at the altitude needed

W/V is wind direction and velocity, normally this would be gained from the MET office but as I am virtual I can set this to whatever I like, I chose a direction of 350 degrees at a speed of 20 knots. The distance (DIST) is measured directly off the chart along each leg of the route.

6 – Calculate the other PLOG entries

Now we need the flight computer – this is fairly complicated and I am not sure yet if I understood the various videos correctly yet. As usual there seems to be many ways of doing the same thing 🙂

To start with, the wind direction is set at the top against the index arrow 350 in my example. The sliding part is then moved to align the blue circle with zero and the wind velocity is marked with a pencil (I enhanced the mark to show) 20 here.

Next, turn the outer ring to show the true track – 39 degrees, as the ring is turned the cross marked earlier also moves.

The wind correction angle is read from the new position of the cross – 12 degrees, as the cross is now to the right of centre, the value is deducted from the value set at the index to give a result of 17 at the index shown below.

The cross has now moved again to give a heading correction value – this is subtracted from the true track and entered as Heading (T) on the PLOG. Looking at the cross, it is now aligned with the arc representing 73 – this is the ground speed – clever stuff.

HDG(M) is the heading adjusted for the earth’s magnetic field and the magnetic deviation of the planes compass, I never knew this was a thing before looking at this stuff. There is a picture below showing the correction lines on the planet, one of them is zero and this point moves West at around 12 miles per year! The chart is marked with what are known as Isogonal lines which show the variation, the nearest to my route is 0.5W this is subtracted from my heading to give me a result of 031.5 – it’s not possible to set or fly a half degree variation so I will take either 32 or 31 degrees. The simulator planes compass has zero deviation so I can ignore this.

Travel time for each leg is worked on the other side of the flight computer. The index on the middle (minutes) scale is set to the ground speed (73), look round the outer ring to find distance (14), read the time off the middle ring (11 minutes 30 seconds).

7 – Calculate fuel quantity

Fuel is fairly irrelevant in a simulator as it can be replenished at any time in flight or on the ground. For the sake of seeing if the calculations work, I’ll try it out.

From the pilots operating handbook for a Cessna 152, the fuel used should be very low, about 5 gallons in all, that quantity does not cater for the extra that would be needed in reality for a missed approach, holding time above the airport, emergencies, taxi from and to parking and so on. In reality, with such a small plane, most pilots would simply top the tanks off before each flight based on what I have read.

At 2000 feet, 2200rpm, 90 knots airspeed, it should burn around 5.1 gallons per hour, my flight is only 50 minutes long (possibly). The initial climb is not counted here as I intend to climb to 2000 feet before passing over Stansted airport and starting the stopwatch. The climb can be included but it complicates matters and as it’s so short for a low altitude flight, not worth calculating. Descent and landing is not included either as I will count the trip a success once I reach Norwich airport.

These values are practically meaningless for a simulator, in fact i’m not even sure it tells me how much fuel is in the tank in gallons, we shall see.

8 – Calculate mass and balance

Again, this point is of little use in a simulator, it won’t let you unbalance the plane by overloading it so it can be accepted that the plane is safe to fly. In reality you would need to know passenger weights and positions, luggage carried and where it is held, fuel weight and lot more.

27 February 2022

Below is my final log sheet for the flight, I have altered some figures following a recalculation so the data above may not match 100% but it was not far off. I forgot to adjust the true airspeed for pressure altitude so that went from 90 to 92 knots, my marking on the wind calculations was a little rough so I tried again. My ground speed should now be about 78 knots which also lowered the timings for each leg, I have also added a “T+” total for the trip on the right so i can see what the stopwatch is supposed to say at each point.

28 February 2022

I had a chance to fly my route today, and blew it 🙂 Rookie pilot mistake – I flew the whole trip following the TR(T) true course heading and not the HDG(M) corrected heading I had calculated 🙂

The result was that by the time I got to the third VRP which was to be passing over Old Buckenham airfield, the airfield was 10 miles to my left side – this is the effect of wind pushing me off course from the true heading and highlights why wind effect has to be calculated and accounted for.

I did manage to find Norwich airfield and land though but it was about five minutes later than planned. Fuel used was around 4.5 gallons which is pretty close to my estimated 5.1 gallons.

I will try the flight again.

1st March 2022

When you use the correct heading, dead-reckoning works! In fact it worked extremely well, better than I had expected.

The wind settings were the same, each VRP check appeared pretty much at the exact time expected and in the correct place 🙂 I did alter course a degree or two at the mid-way point but it was minor and wouldn’t have affected things too much if ignored.

I reached the destination 1 minute ahead of schedule – not bad for a 50 minute flight in strong winds. Fuel consumption was spot on, I used 4.94 gallons and the calculations predicted 5.1 gallons.

Next up, I’ll plan a trip with multiple legs and see how that works out 🙂

2nd March 2022

I planned a two-leg trip today, departing Lands End airport, travelling south-east passing RNAS Culdrose base to pass over the Lizard and Predannac MOD airfield then turning North over Falmouth, Truro and landing in ST Mawgan airport. Only about 35 minutes but very windy at 20 knots which made landing at St Mawgan fun as you have to fly out over the sea and come back in to land, the cliffs really throw up some turbulence 🙂

Dead-reckoning worked perfectly again, fuel used matched the calculation, time was only 45 seconds out and the arrival airport popped into sight right on schedule. I know this area well as we holiday down there a lot so the towns and wind-farms looked pretty familiar.

3rd March 2022

I never realised until I started this venture that the humble wind sock is more than just a direction indicator. It is calibrated to show the approximate wind velocity in knots!

Based on where the sock turns from downwards to roughly horizontal, the wind velocity can be read by looking at the joints between red and white sections as shown above.

4th March 2022

I tried a few things out today – a three-leg trip and I turned on live weather as well. In the simulator, live weather downloads the real weather forecasts and attempts to reproduce the same effects in the simulated world, mostly it does a pretty good job as well.

My route started at Exeter airport, went North east to pass over Merryfield airfield, turned East to fly to Compton Abbas airfield, then North east to land at Boscombe Down military airfield. Total distance was 71 miles and time estimated at 45 minutes.

The weather reports I downloaded to plan my trip gave me winds of 330 degrees at 20 knots so I used those figures to plan my course corrections. However, when I loaded the route in the simulator, the winds were reporting 350 degrees at 15 knots – clearly a little different but not massively so.

I decided to reduce my corrections a little to allow for the slightly lesser wind speed and direction change. The first leg worked well and i passed over my turn point on time and in position. I think the second leg was the failure, by the time I reached the turn point at Compton Abbas, I was off course fairly badly and could not find the reference points at all.

I continued on the same course for another 5 minutes or so but it was becoming clear I was lost. The only thing to do was turn to the last leg heading and try to pick up a new reference point – reading a low detail map and flying a plane is no easy task! In the end I tuned the com radio to the tower at Boscombe Down and requested a direction fix, it turned out I was about 10-15NM past my last turn point and off to the South east of it.

The airport turned up nicely when I had travelled a bit further, the time lost was about 15 minutes so I was still well within safe fuel limits and the landing went well 🙂

I’ll stick with live weather for the next few trips as it adds a bit of unpredictable result to the fun and is more realistic as well.

6th March 2022

Nice little trip along South Wales coast today, live weather again just to keep things interesting. Departure was Bristol airport, across the channel, make land at Barry and over to St. Athan airfield then up to Swansea airport passing Porthcawl on the way.

Although fairly windy, the weather was lovely and clear and the 35 minute trip was over with me running 3 minutes late. Having live weather makes visual reference points far more important as the wind I download from the MET when planning is always just a forecast and never 100% correct by the time I fly. Today I could see the winds along the Bristol Channel had blown me off course but as Barry is pretty easy to spot I could change course mid-channel and hit land on the correct heading.

The second leg of the trip was equally off a little but again, easy to correct and apart from some buffeting wind when crossing land/sea borders the trip was smooth and fun. I think the wind angle was pretty much the same as planned but the velocity had dropped from the reported 20 knots to maybe 10-15 knots so I was drifting inland on each leg, this all highlights why small aircraft are generally only flown in clear weather – VFR means you must be able to see the land clearly, with no instruments as such to help, losing sight due to clouds or fog can be very dangerous.

7th March 2022

One more trip today, last one for a while. Nice little jaunt along the south coast, took off at Lydd, down to Eastbourne/Beachy Head, up to Shoreham, then across to Selsey Bill and over to the Isle Of Wight to land at Bembridge airfield.

As before, the winds had changed between forecast and flight but being able to follow the coast makes it easy to fly. The hard part was trying to find Bembridge airfield – it’s tiny and only has one very short runway with no tower so I could not ask for directions. In the end I did find it and managed to make a bumpy landing after a couple of go-arounds. The wind on the Isle Of Wight had changed a lot and was a struggle to get down in, should probably have diverted to Sandown airport.

The trip was 82 miles and took 55 minutes.

14th March 2022

I fancied a change so I upgraded my plane to the next model – the Cessna 172 Skyhawk. This model is larger, more powerful and has a computerised ‘glass’ cockpit display. This upgrade now gives me a nearly full autopilot and the ability to try instrument or ILS approaches etc.

Having only done visual rules flying so far, changing to an instrument approach in poor weather is quite a shock as you simply cannot see anything outside! The picture above is from one of my test approaches into Stansted airport, it did work and although a little bumpy due to winds, I landed successfully.

Here is a short video of an instrument approach at Stansted again, there is no ‘auto-land’ feature on small airplanes so you use the instruments to get close and then turn the autopilot off and land manually. If the weather is poor and the clouds do not break before you reach your minimum altitude you would have to abort and divert to another airport as at that point visual rules take over again and you need to be able to see the runway fully.

As the 172 Skyhawk only has a partial autopilot, you still have to manage things like the throttle and flaps yourself so it’s not a ‘sit back and relax’ type of system.

18th March 2022

Playing with all the new features in my plane, I thought I’d have a go at VOR navigation. VOR stands for VHF Omnidirectional Radio, a transmitter that is capable of sending out a pattern of signals at specific angles relative to North like a cartwheel, as seen below.

In the centre is the transmitter, and a large circular aerial array like the one shown below, these are dotted about all over the UK and also in most other countries too.

By using the VOR receiver in the plane, these radial signals allow you to navigate from one VOR to the next, in any direction, you can also use VFR methods to pick out landmarks on the way to verify your course. It’s a pretty simple task but difficult to explain in detail, a good explanation can be found here.

I set myself a simple trip from Manchester airport to Birkenhead and on to Mona airport in North Wales, in the picture above, I’m just passing over Birkenhead. The route is marked a little poorly below but can just be seen on the map with a thin black line.

You can fly a VOR route manually as the system was around long before autopilot was common, I did my little trip this way, or I could have just turned autopilot on and had it follow each radial for me. Changing radial or course is a matter of tuning the heading indicator for the new course/radial and then ‘picking up’ that radial until the indicator shows you on the correct heading.

If you were completely lost, had a map, a pen and maybe a friend or co-pilot you can also use VOR radials to triangulate your position fairly easily, with autopilot turned on and flying the plane, a lone pilot could easily do this.

19th March 2022

Restrictions! I thought I’d go back and do another VFR dead-reckoning planned flight today, nice and easy North Weald airfield to Duxford airfield. This time I observed airspace restrictions though.

In the chart picture below, the red line shows the easy but not allowed route, it goes through the Stansted CTA or Controlled Traffic Area restriction, to traverse this area I believe requires a lot of permission, flight plans and finger-crossing as it covers the area used for approaching/departing commercial air traffic. The arrow, bottom left is the wind direction.

My next option is to skirt around the Stansted CTA, the black lines show my chosen route – North Weald – Chelmsford – Halstead – Haverhill – Duxford. It’s much longer but requires no permissions as long as I stay below 1500 feet at the start and also take care at the red circle area (Haverhill) which comes extremely close to the CTA – I diverted further North here to make sure. The red blob is Earls Colne airfield which is another area to avoid, best to contact ATC there and announce my passing close by.

The trip worked perfectly again, It’s very satisfying to plan a route and have it all work well. From what I have read, straying into a CTA is a very serious and possibly dangerous issue, not sure what the punishment would be though.

20th March 2022

I tried a GPS autopilot night-flight today, Southend airport to London City Airport. I used GPS planning with autopilot when possible, also used an ILS approach for safety at London City – it’s a fairly steep descent.

It was great seeing the lights of Essex and London on a clear night, I did use ATC but made a mistake and requested a normal VFR landing but then used an ILS approach so I got told off upon landing as I used the wrong runway, oh well…

In real life I could not have done this as I am not instrument or IFR certified, only visual or VFR so far.

29th March 2022

Just for comparison and fun I re-run my flight from Southend to London City in the daytime, I still used GPS and an ILS approach even though it was clearly VFR conditions, I paid for the flight computer so I’m going to use it, right 😉

15th April 2022

It’s been a while so I thought I would plan a short VFR flight and do it without autopilot & GPS. I decided on the route shown below…

Starting at Compton Abbas airfield, I headed towards Boscombe Down airfield, then down towards Southampton to fly over the city before picking the 092 radial towards the Chichester / Goodwood VOR to land at Goodwood airfield.

The wind was pretty high as it makes things a little more tricky, I set it to 240 degrees at 10 knots, 2500 feet. Both airfields were grass runways and fairly short at around 800m, spotting a grass runway from the air is very difficult.

Each leg of the trip worked well, timings to each checkpoint were within a good tolerance and after a few circuits over the Goodwood runways to try and figure out which one I was looking for (it has three runways giving six landing options) the landing went very well.

A video of the trip is here..

16th April 2022

I decided to fly my Compton Abbas to Goodwood trip again, this time I programmed the exact same trip into the flight computer. I still did all the flying manually but this time I could compare my route to the computed route using the GPS display.

In the cockpit views of the video below, the route is shown as purple on the right-hand display. The first leg, Compton to Boscombe Down was a little off, it seems I over estimated the wind blowing me off course and as a result I was running about 5 degrees off.

The second leg, Boscombe down to Southampton went very well, the crosswind was strongest on this leg and the calculations I made seemed to be just about right. The last leg was to pick up the 092 degree radial from the Goodwood VOR, maybe I could have chosen the 095 radial which would have been nearer the computed course but it does not matter as when tracking VOR radials you will always reach your goal.

The landing was a little less than decent but pilot and co-pilot walked away comfortably and the landing gear was not damaged, finding grass runways is pretty difficult 😉

17th April 2022

Sightseeing trip today, a small executive airport near Florida City down along the Keys to land at Key West airport. I never realised how big the keys were – it took me over 90 minutes to fly, using the main road to navigate, very low level at 600 feet, I used autopilot to manage the altitude but controlled direction manually using the heading control function.

8th August 2022

I’m still flying, currently in the TBM930 single engine turboprop. Been busy on other hobbies, having a holiday and also awaiting an update to the software to hopefully iron out some annoying bugs that are making trips unreliable and not enjoyable, these crept in on the last update and caused a good few issues for many users.