Question for mil pilots: DIY IFR approach legality in emergencies?
 

I was reading a book called Viper Pilot and at one point in the book, the author talks about an enormous sandstorm wrecking visibility at all nearby airfields. The tankers flew off to alternates and were too far to provide refueling and his entire flight was in an emergency fuel state. The only alternates not engulfed by the sandstorm were beyond their max range at their fuel state.

In the book, he describes flying a dry run over a runway while he still had enough visibility (I think it was about 1/2 mile at that point), and he set a steerpoint over the runway as he flew and sent the steerpoint to his flight via the link. He then did a pattern and landed, with the visibility dropping to something like 1/4 or 1/8th of a mile. The whole flight landed safely by following the DIY approach.

So, this technique actually works quite well and probably saved the flight. I tried it in the Falcon BMS sim and it worked a lot better than I expected.

But what is the legality of this in the military? Would you be in doo-doo for allowing your fuel state to get so low? And how does the military react to this kind of DIY instrument approach if conducted in an emergency like as described?

I suspect, in your example, the pilots would have been congratulated for saving $$$m in combat aircraft but investigated as to why they were in that situation in the first place.

Paradox,

In my fleet (military) we routinely train to carry out such an approach using internal aids. It's not 'legal' as such, so we don't carry it out IMC live flying for training. The key point is that military flying in an operational context has a lot of variables that are not as easily controlled as in a peacetime context and a lot of your 'options' can be pulled from under you pretty quickly.

The procedure we use is fairly similar to the one described. If the airfield has a published approach we'll always try and mimick that in the kit, but if it doesn't I can have a look at the map, have a best guess and design what is effectively an RNAV/ point in space approach on the fly.

Our chain of command would certainly have no issue with us doing the above if there was no option, though there would hopefully be a review process after the fact to understand why we were forced into it and to try and prevent it happening again.

it comes firmly under the heading of Emergency Let Down - not something you would do in normal circumstances (except to train for it VFR as pba says) but available in extremis as a far better alternative to running out of fuel.

Having said that, we are moving towards precision based nav and more GPS-based approaches.

In the forties there used to be a piece of kit in Air Traffic called a 'Porka'. This was a miniature motar and would fire a flare vertically when required.

Should the airfield be socked in with fog then an aircraft would get steers to the airfield at 1,000ft. Just before he reached the overhead they would fire the Porka so that the pilot would see where the tower was. He would pass it and carry out a timed circuit: Rate one turn/one minute/descending Rate one turn, that hopefully would have him on finals at 2/300 ft. in a position to see the runway.

They were out of date when I started but we were still taught timed circuits. Seemed to work OK.

the modern version is the WRAF assistant but spelled with an er at the end:E

DF homing to the overhead was always available if the instrument approaches weren't available and the same concept was used for emergency letdowns in the AAC where the troops on the ground would listen out for the aircraft in the overhead and transmit to the aircraft - a timed turn teardrop procedure would then be executed to let down to the 'overhead' on a 'safe' heading. Not very precise but it could work well if the terrain was suitable.

Never heard of the Porka ... YLSNED

DF could be a good get-you-down provided that the antenna was in a decent position relative to the runway. However, the brick blockhouse was usually well offset to the side, so a straight homing to the antenna would put you on the grass. I did try, in my intensive DF days at Strubby, of doing an inbound homing on a very slightly offset heading, and then kicking off the angle when the pilot called [on request] Outer Marker which was on the coast a bit south of Mablethorpe. In theory that had him roughly on the centreline with 3.5 miles to run. Safe enough over the flatlands of the Lincolnshire coast, but far from an exact science!

We did a lot of time-related procedures back then, which is why the Approach Controller was always equipped with a pair of HM Stopwatches - as indeed was Local where a DF display was fitted.

Salute!

Plenty of ways for successful do-it-yourself approaches unless the vis/ceiling is like a hundred and a quarter or 200 and a half.

The old ways used DF by tower and your own radio gear ( flew two jets with DF radios, and one was fielded in 1971, plus had better avionics than the original F-16I I flew 8 years later),

The use of the inertial/GPS nav gear plus a good ground map radar makes a non-precision approch fairly easy, even if not practiced. In Thailand during one of the monsoon seasons, the haze was so bad we could not see the field from 1500 feet and 4 or 5 miles. So we used radar and nav gear to align with the rwy for an overhead pattern.

With the HUD in the Sluf and Viper you set tgt elevation, so your tgt "box" ( TD symbol) is very good. Can update position using the radar. So now you can have a symbol at the end of the runway and the correct elevation. We used this to start descending 100 miles out and simply placed our flight path marker over the box. Duhhhh.

So Dan had to enter the position of the field that had not already been entered as a destination. We used to "mark" the ramp or end of rwy at home base to use later, or we could manually enter the coords. So getting an accurate pos for a "strange" field using a flyby nav update seems a good idea. Can use radar to get the TD box there and then refine the coords with the overfly nav update.

The Sluf had that magic map, so you could refine your nav position using radar, then designate your destination on the map to get the TD box and steering.

Gums sends...

Remembering of course, that there is always enough fuel during an emergency let down to get you to the accident site.

Helicopters:

1970's.
Decca moving map - very dodgy but works for supertankers.

1980's.
TANS (Tactical Air Navigation System) used Dopplar cross refer TANS to a radio beacon and update 'FIX' (DME/TACAN) in the overhead, followed by a set pattern to parallel the runway outbound at 1.5nm offset to begin a turn in at 7nm from the threshold. Pretty much an SRE talkdown but internally from the crewman.

1990's Super TANS / RNS252 (Racal nav system) - similar to above but GPS input replaces dopplar. GPS less likely to go walk about than dopplar was. FIX could be offset as long as TANS and other radio aid agreed with one another. Pattern was the same downwind at 1500'agl IIRC.

Deep doo doo:
Radar Altimeter monitored let-down ideally over the sea. Wind farms and gas/oil rigs make this very iffy.

and/or
Establish hover on the Rad Alt at a pre determined height and get crewman to open the door and look down - why? - because slant vis (pilot) is not as good as vertically down (crewman); and this procedure may just prevent you wearing a wires necklace in the event of high tension wires being nearby.

Practised all of the above weekly and used it once:- In Belize after Radar (SRE) piped up "Loss of radar contact due to radar clutter (weather)" just at the time when we needed ATC more than ever and options were few if any. In fairness we were already halfway down the approach at 3nm+ when this event occurred. The rain was so heavy that having the wipers on was a wasted effort. On an ILS/PAR/SRE the TANS/GPS was always set up to act as a back-up.

Not forgetting the good old Decca let down (without the moving map). I never really understood how it was done, but thankfully most of the crewmen did!

Apart from the one who decided to offset one lane to the left to allow for the crosswind:ok:

And the one over the sea who confused the depth contours and the Decca lanes...

I recall that in the Tornado F3 we had an MDA in the Release To Service for Internal Aids Approaches using the Radar and Main Computer position. IAAs were practiced IMC on normal training sorties. They were normally monitored by ATC but not sure if that was a legal requirement?

Many moons ago before the days of "rules for everything" we used to perform a self navigated QGH pattern using Rebecca/Ureka in the Jet Provost. I cannot remember what minimums we used; about 1000ft I think?

In the '80s the SHAR had an internal aids let-down that worked very well; lock mother with the cloth co*k, enter the flying course and select PIA (pilot interpreted approach); the HUD then gave centreline and glidepath together with cues for hover-stop and braking-stop to get you alongside in the hover. Only snag was flying a very unstable jet at 140kts with 60 nozzles. I forget what the official limits were but it was proven down to 200' on occaisions, when flying non-div. Sorted the men etc!

Off to practise my turn-backs.

Out in the Solomon Islands we had a GPS letdown.. We didn't have the full kit to do approaches, all we could do was similar to an NDB. This was necessary because of the weather and terrain we had to fly over the top of cloud covered mountains and let down the other side. The Chinese registered aircraft I had flown turned the beam bar automatically when a new track came up but the Bristow cheapies did not.

A case in point was the approach to Kwaimbaambaala. This was a 'airstrip. that was the other side of a mountain with an approach from the northwest. One had to go over the top of the mountain at around 6,000 and let down the other side and do a GPS approach.

The GPS would track you on base leg directly back at the mountain you had just crossed. You would sit there following it with your radar gradually turning red as it filled up with rocks. You would keep ranging it down fully depressed and even at 2.5 nm, it was painting at the top. The steer bar would twitch as you came on the approach track and you would input a screaming max rate turn to the left through 120 degrees and reset the beam bar so that you recovered to the centre line pointing away from the hills.

When you broke cloud you were then reminded how big and how close the hills were on the right hand side.

The things you do for money.

In Vietnam War Years....using Army operated GCA sites for "Radar Navigation and Approaches"....during Monsoon Season the dreaded words..."Radar Contact lost...Resume own navigation!" were a certainty upon being in solid cloud...much less Monsoon Rains.

I always wondered what method they thought we would use upon being told that as there might generally was not an operable Nav Receiver aboard any of the Helicopters.....assuming the NDB's might be working....which they usually were not.

Very interesting hearing all these 'cockpit perspectives' for getting down. I though ATC was indispensable, but clearly not :)

Still in existence, had a discussion about them a while back when I was on gardening leave, :E as someone was asking what they were, various ones are still dotted around the Country, this one is in the New Forest

Metal socket behind the concrete Airfield pundit code - identified as a Signal Mortar. Photo taken August 2013.

And this one at Beaulieu

WWII Hampshire - RAF Beaulieu airfield:... (C) Mike Searle :: Geograph Britain and Ireland

http://www.geograph.org.uk/photo/5312611



http://www.newforestheritage.org/upl.../large/847.JPG

I find it surprising that no one has mentioned the internal aids approaches that we used to carry out on the V Force. It is entirely possible that these were also carried out earlier on other types equipped with H2S. Maybe someone could confirm this?

YS