"search aircraft questions" Topic

How far can a search pilot see? That is, while flying his route in fairly good weather at some reasonable time period average flight height, how far to either side of his plane is he likely to see an enemy ship? Also, do they fly a straight path out from their base or fly some form of pattern to cover more surface area to either side of the mean route.

How far an observer can detect a visual target (in a forced-choice experiment with an uncluttered fixed scene, but assumed to be true more generally) depends on:

The target size (apparent size, allowing for any magnification)
The target contrast
The level of ambient light
The sky/surface contrast ratio

Given that those variables can all vary over wide ranges, it would be absurd to attempt to take a single figure as generally true.

However, to give an idea of the sort of magnitudes expected, one historical survey, USN ASWORG memorandum no. 20, published on 07 Dec 1942 (available at the public records office under piece number ADM 219/549, "Analysis of US aircraft attacks on U-boats"), gives the average diostance at which U-boats were sighted by search aircraft as 4.3 miles, with an average met vis of 7.6 miles, and the ranges of detection apprently following a negative exponential distribution (thus showing the highest degree of variability). THis is in tolerably good agreement with the "folk rule" among ground visual sensor modellers that visual detection is normally limited to half met vis.

As for the patterns flown, there are loads of them. Apart from line searches, box searches and so on, Coastal Command used to have a selection of fixed search patterns when flying air escort with splendid names like "Lizard", "Mamba", "Python", "Serpent", "Adder" and "Viper".

All the best,

John.

As noted, depends upon the size of the vessel.

A carrier, or battleship will be much easier to find, than a smaller vessel, and if they are moving fast, e.g. trailing large wakes, that will make things easier as well.

Not sure on the search distances for other vessels. I imagine Command at Sea, or other rules should have some decent data for you.

Yes, they would typically fly straight out on their search pattern, and them search in a grid where they might expect any targets to be, e.g. flying roughly parallel doglegs, of various lengths.

Are you asking about a search aircraft or the pilot of a single engine aircraft?

A pilot may have to rely on the human eye, a search aircraft will often have a crew member with binoculars.

Large ships often have a screen of smaller ships giving the pilot a breadcrumb trail to the best targets.

In theory, the higher you go, the more you see. The reality is quite different. There are damn few days where the sky is not filled with various types of clouds at a myrid of levels.

If you fly below the clouds, visibility is about 10 miles or so. If you fly higher you increase the theoretical visibility, but if you go above a layer of even scattered clouds, your coverage is significantly less than 100%, and you risk missing quite a bit of ocean.

Big recon planes, which are easily seen in the air (especilly on a background of clouds) and vulnerable to fighters, tended to fly lower. USN carrier planes often flew higher if the clouds allowed.

Ships were also sighted more often through their wake being visible than the vessel itself. This also applied to submarines. The faster the ship is travelling the longer the wake and the whiter the bow wave.

A few years ago I was having breakfast on the quarterdeck of a cruise liner…and of course being a wargamer…. could not help but reflect on how extensive our wake was, on what was in all other respects a very dull morning.

Ships were also sighted more often through their wake being visible than the vessel itself. This also applied to submarines. The faster the ship is travelling the longer the wake and the whiter the bow wave.

A few years ago I was having breakfast on the quarterdeck of a cruise liner…and of course being a wargamer…. grin could not help but reflect on how extensive our wake was, on what was in all other respects a very dull morning.

It is amazing how visible wakes are. Often when crossing Lake Michigan at airliner altitudes (22000-27000 feet) it is easy to spot the wakes of even fairly small craft (e.g., charter fishing boats). Big stuff (lakers and salties) will leave wakes miles long. this will, of course,be lessened by rough weather.

Rougher weather, Force 5 and above, apart from being accompanied by heavy cloud cover, will break up the wake of even the biggest ship in very short order.

Indian Ocean and mid latitude Pacific Ocean would offer significantly longer visibility than the Atlantic, especially North Atlantic, in any weather.

The wakes have it. I've spent countless hours in S-3's looking for ships/subs both visually and with radar/flir at all altitudes. You almost always see the wake first, especially with submarines. But it is a complex interaction of weather, altitude, target size, target speed etc. The best source that I have found for modeling that is in the CaS/Harpoon rules.

Paul

That's an impressive endorsement!