Mind the gap

HMS Queen Elizabeth delayed sailing today due to strong easterly winds in what is a good example of risk-vs-operational imperative decision making. The following short read is a counter to the resulting ‘what if we had to go to war and it was windy’ commentary.

Let me start this by saying I have only ever berthed an aircraft carrier once, by which I mean I dumped HMS Ark Royal somewhere in the middle of Portsmouth Harbour and the pilot/tugs did the rest. However, I did drive other warships of different shapes and sizes on many occasions, so let me give this a go.

HMS Queen Elizabeth (like many warships) has two propellors (at the stern) and no thrusters at the bow (or stern). This gives you plenty of control (and power) going forwards and backwards, and you can turn on the spot relatively easily, but you have no lateral control (unlike ferries, cruise liners and some merchant vessels). Because of this, wind on the beam is not always your friend. If a ship is stopped in the water, it will move sideways at approximately 1 knot for every 10 knots of wind. Today’s easterlies would therefore have generated in excess of 2 knots lateral movement to the west for QE thus potentially setting the ship down rapidly onto what used to be HMS Dolphin (circled).

Portsmouth Harbour Chart

Unfortunately, there isn’t much that can be done about this. As a ship speeds up the lateral effect of the wind does decrease but it doesn’t disappear entirely. In open water you can counter the relative motion by ‘aiming off’ (into wind) by a few degrees but the entrance to Portsmouth harbour is too narrow for this with a ship the size of QE: any angle off the planned deep-water track would see her bow/stern unacceptably close to shallow water.

The gap is very narrow for QE. Available water is narrower still.

Tugs, like thrusters, start losing their effect at speed as well. They can control the ships head and stern and if necessary slow you down but as soon as you are underway, their ability to control your lateral movement reduces with every added knot. This can generate a dilemma as a warship captain because the speed you want to lessen the effect of the wind makes the tugs, in turn, less effective.

There is some good news though. The Queen’s Harbour Master team in Portsmouth are as capable of controlling warship movements as any team in the world. The tugs procured specifically for moving QE around are extremely powerful and well handled. Also, the wind limits will have been made into a science by now (see diagram). Clearly a wind on the beam is worst case (1). From dead ahead (in this case from the South) within reason, is fine (2). Wind on the bow, such as a sou’westerly, will have some effect but not as much (3). Same as a wind on the quarter (4). Wind from dead astern, less still (5). All this will have been calculated and clear limits articulated, i.e. 25 kts from the east: out of limits, 20 knots from the southwest: just in limits etc.

Good ship handling is part art and part science. One must know what the conditions should be doing to your ship, see what they are actually doing then have the confidence to drive a very large and expensive warship accordingly. One should always retain something in reserve. Every Captain has at some point or used up their reserve and retired to their cabin for a stiff drink after what appeared to everyone else to be a punchy and successful alongside. If you don’t build in this margin you will eventually come unstuck; embarrassment, injury, large bills, programme delays and Courts Martial follow quickly, often in that order.

So back to QE. A strong Easterly is worst case and today, the science would have determined that the risk of the ship being set onto a lee shore was too high. The art, and where the Captain earns his pay, is to balance this risk against the operational imperative to sail. Today, it was for an exercise so it made absolute sense to wait – live to fight another day. Delaying sailing is never comfortable because expectations are high, programmes are taut, expensive bits of kit are waiting to fly on and, if it’s a long trip, family expectations have to be managed, but, every single peacetime incident has ‘needlessly pressing on’ somewhere in the investigation report. Besides, the wind always dies down in the end. Sail when it does and then just ring on a couple of extra knots to catch up. Push it in peacetime and one can end up alongside the Still and West at which point everyone gets very cross. It happens…

HMS Vanguard making an ‘unplanned visit’ to the Still and West in 1960

But to those saying ‘so we can’t go to war if it’s windy’, yes we can: the captain just has to adjust his margins accordingly which, of course, is his job. He does it 100s of times a day, every day, with billions of pounds worth of kit and over 1000 people relying on him to get it right again and again and again.

All captains do.

One thought on “Mind the gap

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s