RAF NDB(A) APPROACHES to RAF ALDERGROVE.


RAF ALGERGROVE EQUIPMENT STANDARD versus HUDSON I EQUIPMENT STANDARD

Within FS9 RAF Aldergrove (EGAA) retains a Lorenz Beam, but in 1940 our Hudson I does not yet have a BABS receiver and cannot receive either the Lorenz beam or any co-located DME. In 1939 - 1940 all of our approaches to EGAA will be NDB approaches. We have no ADF. Lots of aeroplanes have no ADF. That is why these are NDB approaches not ADF approaches. 

Nobody needs automatic anything to fly NDB approaches. Each time we are inbound to the OY NDB (which transmits on 332 Kcs) we will be using our obscured arc crossing needle pilot goniometer to locate the OY NDB. Each time we are outbound from the OY we will use our clock to fly timed outbound legs along mandated magnetic courses. In between each inbound and outbound leg we will use our turn and slip gauge to achieve RATE 1 (3 degree per second) one minute duration 180 degree turns from inbound to outbound and vice versa.


ALDERGROVE 2008 INSTRUMENT APPROACH PROCEDURE (IAP)

Make sure you have the supplied EGAA IAP in pdf format on screen as you read on. If you do not already have it you will need to download the free Adobe Acrobat reader from the web in order to display real world approach plates. Double click the pdf file to open it. Size it using the zoom function in the menu bar until you can see the whole page. Zoom in later if you need to.

There are slight differences between the procedure depicted for use in 2008 and the procedure we will use in a Hudson I in 1940.


MINIMUM ARRIVAL (phase) ALTITUDE at the INITIAL APPROACH FIX (IAF).

In 1940 we will normally be returning to Aldergrove from a patrol ahead of an Atlantic convoy to the north west, but it makes little difference since from any direction during our WW2 arrival phase we will always descend to only 3500 QNH inbound to the Initial Approach Fix (IAF) which is the OY. 

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Arrival = Descent phase:

VSI   = vary to deliver
IAS   = prior cruise IAS
MAP   = OVERSQUARE (follow RPM down)

Prior to IAF, hold or circuit:

MAP = OVERSQUARE (follow RPM down)
VSI = 0
IAS = 135 MIAS
****************************


ESTABLISH IN THE OY HOLD (teardrop entry).

After we first cross the OY we will usually be required to join the holding pattern which is a one minute race track aligned 250M inbound. If approaching from the east, which would be unusual, we arrange our arrival to arrive already tracking 250M, ready to turn right at RATE 1 over the OY to go outbound 070M for *one* minute before turning right RATE 1 inbound 250M again. Once we are established in the racetrack hold, flying RATE 1 TURNS (= 1 minute per 180 degree course reversal), causes each hold to take four minutes.

More usually arriving from the west, as we cross the OY we turn left 052M for *two* minutes and then turn slightly more than RATE 1 right (198 degrees) to inbound 250M. In all cases we have achieved 135 MIAS before we first reach the OY and we sustain 135 MIAS (flap up) in the OY hold while we are instructed to hold.


MINIMUM HOLDING (phase) ALTITUDE

In all cases *after* reaching the OY (our IAF), and potentially while still establishing in the hold via a tear drop entry, we descend to 3000 QNH at around minus 600 VSI. These procedures separate us from the departures from both RAF Aldergrove (EGAA) and RAF Sydenham, (EGAC is now Belfast City Airport), which (during WW2) are potentially climbing to 2500 QNH (in cloud) via the OY and maintaining 2500 QNH until laterally beyond the OY approach holding area. Without ATC radar control approach delays are not solely due to prior inbounds.

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Holding phase:

FLAP  = UP
IAS   = 135 MIAS
MAP   = as required
Plan  = 300 PPH     

HOLD until < 15,650lbs = MLW
****************************


MINIMUM DESCENT ALTITUDE (approach phase).

We fly the OY holding pattern at 3000 QNH until ATC are satisfied there are no outbounds in confliction, and then we will be cleared by ATC for our approach to EGAA. During WW2 it will be an NDB(A) (Airfield) approach to the entire airfield, *not* an NDB approach to a specific runway with the intention to land 'straight in' on that runway.

RAF Aldergrove is 268 feet AMSL (QNH). The visual circuit patterns are at 1250 QNH. In very bad weather, with no traffic in the visual circuits, our circle to land MDA is 800 QNH mandated by ATC. 

On most days however the cloud base is above 1250 QNH, the visual circuits are busy, and we self impose an MDA, (just) below the reported cloud base, and above those busy visual circuit patterns. The intention is that after we are below cloud, we will maintain our self imposed MDA,  while we positively identify all the traffic in the visual circuits, and especially the specific aeroplane we are cleared to land behind in the landing sequence. 


IMPOSE USER (ADVANCED MENU) WEATHER for training.

During training we should assign 4/8 cloud from 1500 QNH to 2400 QNH and self impose an MDA of 1400 QNH together with a visibility of 10 miles. Only when we are more experienced we will train at night and with rain, then snow, showers below the cloud and much lower visibility. Only very experienced FS9 users / real aircrew should attempt approaches to the real world 800 QNH circle to land MDA with 8/8 cloud and the cloud base at 900 QNH and lower visibility.


DELAYED APPROACH.

The normal situation is that we will commence an approach having already established in the OY racetrack holding pattern at 3000 QNH. We may be anywhere round the racetrack when we receive approach clearance.

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Approach then Circuit:

Before descent to MDA:

IAS  = 135 MIAS
FLAP = UP
***************************
On Descending to MDA:

MAP = trickle barely oversquare
IAS < 155 MIAS
****************************

We proceed as though we were still required to hold, but now that we have approach clearance we can descend below the minimum safe holding level in the OY hold, (because there are no more outbounds via the OY at 2500 QNH). 

Although we have self imposed MDA = 1400 QNH it is not yet safe to descend to MDA. We have two prior altitude restrictions to comply with before then. 

On reaching the OY again our WO reports beacon outbound to ATC. We turn right RATE 1 to 070M again. We are already descending from 3000 QNH to 2470 QNH at minus 500 VSI. 

***************************
On Descending to MDA:

MAP = trickle barely oversquare

IAS < 155 MIAS
**************************

We never allow our profile drag to exceed Vle = 155 MIAS during an approach procedure, (that is going to be followed by a visual circuit), because we may need (or choose) to extend our MAIN GEAR to expedite descent. 

We are required to descend at a minimum of minus 500 VSI within holding patterns. We choose to descend at the minimum ATC compliant rate, to restrain our profile drag < Vle = 155 MIAS. We reduce MAP, but we must run oversquare, and with c/p screws our RPM rises as our windmill drag = IAS rises. With only c/p screws we must also restrain windmill drag = IAS, so that we can restrain MAP.


ALTERNATIVE PROCEDURE.

Now look down to the bottom of the real IAP. Note the ALTERNATIVE PROCEDURE. Note the dotted line extension of the racetrack holding pattern. It is present to cater for all vintage era aeroplanes, not just Hudsons. Vintage era (combat) aircraft may be 'strong' when they are in clean VG configuration, but often they have critically low profile drag GEAR (leg) extension limits (Vle) and even lower FLAP profile drag extension limits (Vfe). 

In a Hudson we must restrain VSI in order to retain the ability to expedite decent with GEAR should we need to. Structurally weak aeroplanes from the vintage era of aircraft history may need to go outbound for two minutes so that they intercept the Final Approach Track (FAT) at least two minutes outside the OY so that they have at least two minutes to descend on the FAT from 2470 QNH to reach 1670 QNH (lose 800 feet) at (or before) the OY (Final Approach Fix = FAF) after turning inbound. 

Whether it is possible to lose altitude fast enough in a Hudson I attempting to fly the standard one minute outbound approach depends only on the headwind on the FAT today, which will be a tailwind while we are beacon outbound. Remember aerial navigation is based on TIME, not speed, not distance. We navigate aeroplanes in 4D with a clock, a compass, and a turn rate gauge.

We cannot depend on a strong enough wind from the south-west, and so in a Hudson I, and most other vintage era aeroplanes, we need to invoke the ALTERNATIVE PROCEDURE. 

We fly outbound 070M for two minutes, not because we need two minutes to reach 2470 QNH from 3000 QNH, but because we will need more than one minute to reach 1670 QNH from 2470 QNH after we manage to establish on the FAT inbound to the FAF.



FINAL APPROACH FIX (FAF) and FINAL APPROACH TRACK (FAT).

Descending at minus 500 VSI we will reach 2470 QNH long before we complete the outbound leg of the approach. The on screen handling notes say;

*************************
When maintaining MDA:

IAS = reduce to 135 MIAS
MAP = oversquare
Look for landing runway
Adjust to circuit altitude
**************************

But we should reduce to, and sustain, 135 MIAS each time we are required to level out in the hold or the subsequent approach procedure.

The RATE 1 turn to the right we fly three minutes after we went beacon outbound, will align us with the FAT, and in nil wind we will be two minutes outside the FAF (OY) as we establish on the FAT. In nil wind our goniometer needles will cross in the middle of our goniometer as we track 250M inbound.

The OY was our IAF, but now we are established on our FAT it has become our FAF. A goniometer will provide no course guidance after we cross the beacon inbound. The whole purpose of these holds and this racetrack approach is to allow us to determine the crosswind today. The crosswind this side of the FAF is pretty much the crosswind on the other side where we will have no electronic course guidance at all, (hence FINAL approach fix). After we cross our FAF we will descend on the heading that made good a track of 250M TO the FAF, in the hope that it will make good a track of 250M FROM the FAF to the airfield, because our obscured arc goniometer needles will be 'off scale' when the beacon our goniometer is tuned to is not 'ahead'. 

We must not descend below 2470 QNH until we are *established on the FAT*. 

Even then we are not allowed to descend to our (self imposed) Minimum Descent Altitude = 1400 QNH. Now we are established on the FAT our descent limit is 1670 QNH until we reach the FAF. 

We are allowed to cross the FAF at or above 1670 QNH, but we wish to cross the FAF at 1670 QNH, so that we can reach MDA = 1400 QNH close to the FAF, so that we can start to search for RAF Aldergrove as soon as possible after the FAF, after we are below cloud at MDA. 

Throughout we ensure that we do not exceed 155 MIAS and we run oversquare. In a perfect world with no wind, and with perfect skill our RATE 1 turn aligns us exactly with the FAT two minutes outside the FAF, but in the absence of that perfection we must still maintain 2470 QNH until we are established inbound to the FAF tracking 250M. With imperfect skill we may have less than two minutes to descend 800 feet from 2470 QNH to 1670 QNH, but two minutes should be long enough, whereas one minute would have been inadequate in a vintage era aeroplane.

Eventually we reach and maintain 1670 QNH and we increase MAP to sustain 135 MIAS.

Of course on some days, and some nights, the visibility will allow us to identify RAF Aldergrove from 1670 QNH while still outside the FAF and many miles away. During approach training it won't because we are now maintaining 1670 QNH in 4/8 cloud whose base is 1500 QNH. It is not safe to descend below 1670 QNH until we become 'beacon inbound' from the FAF.


BEACON INBOUND (from the FAF).

As we cross the OY for the last time (the FAF) we initiate descent to (self imposed) MDA. We descend at minus 600 VSI to 1400 QNH just below the cloud base. We reduce MAP (but oversquare). 

Now maintaining self imposed MDA = 1400 QNH just below the cloud base, and crucially just above visual pattern altitude, we eventually locate and identify the *landing* (most into wind) runway, and all the traffic in all the visual circuits, and all the departing traffic leaving the circuits, and only then position to join the correct visual circuit for the correct runway behind the correct aeroplane ahead of us in the landing sequence. 

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When maintaining MDA:

IAS = reduce to 135 MIAS
MAP = oversquare
Look for landing runway
Adjust to circuit altitude
**************************

We conduct that visual search exactly like a maritime patrol search at 135 MIAS. Elsewhere on another night we may be searching for the lights of a satellite airfield not the airfield we have approached. In any event we must not confuse RAF Langford Lodge with RAF Aldergrove. By always approaching from the FAF for Aldergrove we make confusion difficult. If we cross the FAF at 1670 QNH and descend below the base of cloud quickly thereafter 9at minus 600 VSI), and we see only one airfield in the gloom as the fog creeps in from the Lough, the only airfield we see will be Aldergrove. From other directions 'who knows' which RAF aerodrome we may be looking at on a dark gloomy night.

After we have positively identified our landing airfield. and then our landing runway, we descend to pattern altitude (= 1250 QNH at EGAA) and we join the correct pattern, at the compliant altitude, approaching from the compliant direction (from the FAF) so that the aircraft in the circuit(s) also know where to search for us as we become a threat to them. 

All of this is done at 135 MIAS in clean patrol / search configuration until just before we join the correct visual pattern. This is *not* a precision approach and WW2 aircraft are not suited to precision (straight in) continuous glideslope approaches, even though some can cope. The procedure for flying straight in approaches in a Hudson I is described in the supplied handling notes and the supplied C/P mini tutorial, but is not described in this mini tutorial.

Many flight simulation enthusiasts fly only always rushed precision continuous glidepath approaches, even in ancient aeroplanes, and wonder why the task is so difficult. Often those aeroplanes are simply not compatible with the procedures (real or otherwise) that flight simulation enthusiasts try to impose on them.

So much for delayed approaches to RAF Aldergrove. Now we need to understand 'no delay' approaches.


NO DELAY = TEAR DROP NDB(A) APPROACH 

During WW2, only for aircraft arriving from the west, and which had no delay to their approach to RAF Aldergrove, the standard and alternate racetrack pattern NDB approaches described above were irrelevant. Aircraft which met the no delay criteria were cleared to fly standard *two minute* 'tear drop' approaches instead.

Arriving from the west if we are cleared to attempt an approach *before* we reach the IAF, we will fly a two minute tear drop approach; but only if we are light enough, and only if our IAS as we reach the IAF at 3500 QNH is low enough. 

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Holding phase:

FLAP  = UP
IAS   = 135 MIAS
MAP   = as required
Plan  = 300 PPH     

HOLD until < 15,650lbs = MLW

****************************
Approach then Circuit:

Before descent to MDA:

IAS  = 135 MIAS
FLAP = UP
****************************

Even if we have no delay to our approach and we are not required to establish in the racetrack hold, the holding phase weight, VG configuration, and IAS criteria still apply. The requirement to arrive at the IAF at 3500 QNH still applies. 

The tear drop outbound 052M for two minutes normally used to establish in the racetrack hold, was also used as a tear drop approach procedure. If we meet the no delay criteria our WO calls beacon outbound as we arrive at the IAF = OY. We fly 052M outbound for *two* minutes as we descend to 2470 QNH, which we must maintain until we are established on the FAT. 

*******************************
On Descending to MDA:

MAP = trickle barely oversquare

IAS < 155 MIAS
*******************************

We descend promptly from 3500 QNH after crossing the IAF so that we can level at 2470 QNH within two minutes, so that we can fly the turn at the end of the tear drop in level flight at 135 MIAS. We will be turning through 198 degrees so we need to turn at just over RATE 1 on our turn gauge while we eliminate slip with rudder using our slip gauge as always.

Once we are established on the FAT, two minutes outside the FAF, everything is as explained above.


OBSTRUCTIONS.

A compliant approach in a vintage era aeroplane takes TIME. They have very weak structures and both VSI and IAS may need to be heavily restrained. At RAF Aldergrove we are lucky. The terrain is hilly, but not mountainous. Note that at RAF Aldergrove we are *not* required to remain within ten miles of the airfield centre, but in many locations with higher terrain or higher masts, or other obstructions, we will be. In many other locations we must remain within ten miles of the *airfield* and that may require us to remain within four miles of the *IAF*. 

Now remember the wind will normally be blowing from the south west (above the Atlantic Gulf Stream) and will normally be blowing us into the high terrain and masts, which even near this RAF Coastal Command airfield reach 1748 QNH well within ten miles of RAF Aldergrove. The cloud base is 1500 QNH today (and often). During WW2 those radar and radio masts have no lighting and we must achieve this at night, in snow showers.

Many flight simulation enthusiasts allow aircraft to wander at will and huge distances from the airfield they are approaching. Hills and masts are not the only obstructions to be avoided during WW2, or in the following classic and modern eras. Prohibited and restricted airspace, (no fly zones), such as R431 near Aldergrove, are commonplace. We are not free to wander through them while approaching an airfield from any direction we please, at any altitude we please. We must learn to approach airfields compliantly, even if we intend to join a visual circuit to land.

Now notice RAF Sydenham (EGAC) which has become Belfast City Airport, about 11 miles east of RAF Aldergrove (EGAA), which has become Belfast International Airport. The downtown airport (EGAC) has its own airspace and approaches not shown on this EGAA IAP. That EGAC airspace is a 'no fly zone' to aircraft whose destination is EGAA, now or during WW2. EGAC also became an operational Coastal Command aerodrome in June 1940, but was home to Coastal Command Fairey Battles performing coastal patrols so that the Hudsons from Aldergrove could concentrate on Atlantic convoy CAP.

When we approach EGAA we are allowed to proceed more than ten miles from EGAA, but we are *not* allowed to arrive or approach south of the line 250M - 070M, partly due to the high ground and masts, but mostly due to RAF Sydenham. The tear drops, the racetrack, and the approach procedures all relate to *obstructions*. many of which are just other people's airspace that we no not have an ATC clearance to enter. Every destination has unique procedures which add immense variety to our flight simulation experience.


COMPLIANCE = VARIETY.

The hobby of flight simulation isn't only about learning complaint operation of a wide variety of different real aeroplanes in accordance with their phase by phase handling notes. Potentially it is more about learning the real procedures for thousands of unique departures, arrivals, holding patterns and approaches, real airfield by real airfield, available as free downloads from the internet;

http://www.calclassic.com/propliner_tutorial_charts.htm

and whose usage is explained within the 2008 Propliner Tutorial; 

http://www.calclassic.com/tutorials.htm

The provided phase by phase handling notes are the way they are, because they explain how to comply with real world procedures. If we fail to use MSFS to learn compliant use of the aeroplanes we download, we miss most of what MSFS has to offer. Compliant use of real aeroplanes in a virtual environment, isn't just about compliance with different handling notes that reflect variation of engine fragility and variation of structural fragility. It is also about understanding how to comply with the real ATC procedures, (of the relevant era of aviation history), those handling notes are carefully written to support. 


TEN MILE LIMIT.

Now imagine that the hills within, and around, the city of Belfast were higher, or had taller masts. We *would* be required to remain within ten miles of EGAA while approaching EGAA. We *would* be required to remain with four miles of the OY. Now imagine a strong wind from the south-west above the Atlantic gulf stream, which is the usual situation. 

Will two minutes downwind from the IAF at < 155 MIAS allow us to remain within four *nautical* miles of EGAA?

Drag and speed are two very different things, but the chances are that flying downwind with a profile drag of up to 155 MIAS our speed will exceed 120 KTS (two miles per minute). It would be both unsafe and unlawful to operate our Hudson I as described above. The procedures would not be unsafe and unlawful. There would however be a maximum IAS compatible with flying those procedures in safety if the hills or masts were higher, and that IAS would be much less than 155 MIAS. It would be less than 135 MIAS.

The supplied handling notes and the C/P mini tutorial provide instruction concerning the need to deploy FLAP early and reduce to 110 MIAS early while flying straight in approaches in a Hudson I, arising from the very low Vfe limit = 115 MIAS of the Hudson I. Try to understand why if our approach was to somewhere else with higher nearby hills and masts we would be required to remain within four nautical miles of the IAF = OY, and we we would be required to employ the 'reduce to 100 MIAS early' procedure (described within the supplied handling notes as a straight in procedure), even if we intended to fly a visual circuit.

We must download, study and apply real world approach procedures as well as phase by phase handling notes in order to experience realism during flight simulation. Some approaches may allow us to retain clean VG status until after we identify the airfield we are approaching, but others will require us to deploy FLAP much earlier to restrain profile drag = IAS much earlier, to restrain speed = KTS much earlier, due to obstructions, which may be physical, or may be a no fly zone, or just airspace allocated to the next door airfield.

The IAS limit for many approaches is very low, that makes high negative VSI impossible without substantial and early FLAP. Just making up approach procedures during flight simulation badly misses the point. The real procedures invoke huge variety and require us to solve problems as we PLAN how to fly a real approach and then try to master the skills needed to execute a plan that is realistic, both in relation to the real obstructions at that unique location, and the real structural limits of the aeroplane whose operation we are simulating. The older the aeroplane the more demanding the planning and execution are likely to be. 

Demanding or expecting flight dynamics which can always fly auto-coupled ILS approaches, from any random IAS, from any random location, badly misses the point. Different aeroplanes have different structural limits, in different variable geometry states, and those limits condition how we must operate that aeroplane, unique location by unique location.


RAF and QFE. HEIGHT not ALTITUDE

In passing note that the RAF used QFE (height above airfield) not QNH (altitude above mean sea level) to fly approaches and that the supplied IAP also provides the lower QFE values, (height above RAF Aldergrove in parentheses), for use by suitably experienced flight simulation enthusiasts familiar with QFE approaches.

To fly genuine RAF QFE approaches to RAF Aldergrove use the Kohlsmann control on your altimeter to wind the altimeter down by 270 feet to 2730 QFE just *before* you leave 3000 QNH. 

Note that the odd QNH values (altitudes ending in 70) in the procedures above are due to the real approaches being flown using QFE (heights) which are round numbers such as 2200 QFE and 1400 QFE. Circuit pattern height is then always 1000 QFE everywhere (in MSFS) and our self imposed MDH becomes 1130 QFE (but we might self impose 1150 QFE instead), and the user applied (1500 QNH) cloud base will be at 1230 QFE (feet above RAF Aldergrove).


CLASSIC and MODERN ERAS OF AVIATION HISTORY.

In 2008 we could use the Lorenz beam (LOC) for course guidance on the FAT, even inside the FAF, (NDB(L) procedure), but only if we happened to have an ILS receiver in our aeroplane in 2008, and outside MSFS many aeroplanes still did not.  

Of course by 2008 other options had been made available for classic era and modern era aircraft, with higher structural limits and higher equipment standards, including use of a left hand hold at 4000 QNH over a Radio Range or Omni Range at the BEL, (located on the airfield at Aldergrove), prior to transitioning to a right hand tear drop approach from the OY, which remained the IAF and FAF, even if classic / modern era inbounds earlier held 059M inbound left hand at the BEL. Those facilities and associated procedures did not exist until the classic era of aviation history reached the UK after WW2, and have no relevance to a Hudson I in 1940.


FSAviator March 2011.








