Story ID: 017
Blog: Aircraft Float Posture and Ditching Considerations
By: Dave Montgomery
Caption: Simply hoping an aircraft ditching will not happen to you is no way to prepare for a successful outcome.
Word Count: 1533
After writing Blue Water Ditching in 2012, I have continued my education on the subject of aircraft emergency water landings by speaking with industry experts in our field. There are several concepts that need to be shared.
To remind pilots of the why, I point out that during the 1940s, 1950s, and even into the 2000s we trained ditching. Because it happened. Today, because of greatly improved engines, fuel systems, electrical grids, pressurization systems, fireproof cabins, etc., the risk has reduced to near zero. Training for ditching has been relegated to the back burner and some companies have pushed it completely off the stove.
Predicting problems has never been easy in any industry, but to say a multi-engine aircraft will never ditch…well a DraftKings, Vegas, or Ladbrokes bookmaker probably cannot figure the odds. Over the years we have always tried to think ahead for the industry, and there are a few situations that could lead to the disaster.
A volcanic ash encounter, for example. The Tonga volcano eruption in January occurred 650 feet below the ocean surface. The explosion lasted nine minutes and 50 seconds sending flying molten rock at supersonic speeds, creating sonic booms, and the ash cloud rose to more than 100,000 feet and expanded to 160 nm wide. I remind everyone that the Ring Of Fire stretches from the southern Pacific Ocean, past Japan, across southern Alaska, and all down the western coast of North, Central, and South America.
Other issues that could result in engine loss are heavy bird encounters, hail, uncontrollable fire, and fuel leaks. We are pilots, and pilots like to know and train for everything that can happen to us and our flying metal tube.
So when was the last time you chair flew or simulator re-enacted the 30 minutes of a ditching scenario?
The first and most important technique I have learned and now teach is this: if you are ever in the position of an off-airport landing or a water ditching, turn on the ELT. Immediately! This should be (although it is not) the first step on every aircraft manufacturer’s ditching checklist.
Modern aircraft are equipped with 406-Mhz transmitters that talk to the satellites. Within minutes after flipping the switch, the robust worldwide search and rescue organizations are looking at you and they see your location, altitude, heading, and speed. Rescue control centers are deciding their next step: call local authorities, launch aircraft and Coast Guard ships, or direct maritime vessels.
Before you land on the water search and rescue authorities have the current sea state, water temperature, tide drift speed, and surface wind direction from worldwide anchored buoys. They even have access to classified data such as "where are navy ships today?" If you flip the switch, you don’t need to relay the same information three times to aircraft overhead, which wastes valuable time.
Second, the greatest aid ever invented for ocean-crossing crews is an application—Ergo Blue—that has been on the drawing board and in testing for years. Today, it works perfectly and should be on every pilot’s iPad. Pilots can enter their coast-out and coast-in points, and Ergo Blue will display in real-time all the ships moving on the water along their route.
If you are on the Atlantic routes, crossing the Gulf of Mexico, en route to Australia, or transiting the Arctic Ocean on your way to Nur-Sultan, Kazakhstan, think about the security of knowing you can find and ditch near a ship. To quote Jim Stabile, CEO of Ergo developer Aeronautical Data Systems, “[The app] significantly expands the ditching envelope…Ergo helps you ditch at night, low ceiling and visibility and gets you as close to the ship as possible to reduce time of rescue.” You have just cut your time in the raft to possibly hours versus days.
Hopefully, soon, the map displays on our flight deck panels will be able to show a new overlay—"maritime"—depicting the ships and oil rigs below us. (Are you listening Garmin, Universal, Honeywell, Dynon, Collins, Thales, etc.?) Here is something you might not know; ocean-crossing ships have transponders just like aircraft, which is where Ergo receives its information. To see what this looks like, visit marinetraffic.com and click on the live map.
Third, while working on my last presentation I compiled pictures of land aircraft ditched on the water. They prove how survivable a ditching is and open a new line of thought about buoyancy and how it relates.
I simplify buoyancy as the battle of float versus weight. Float occurs as the fuel tanks have some air and are trying to hold the aircraft on top of the water. Weight is trying to drag the aircraft under. It is a battle to see who wins.
As I pondered the pictures I focused on what was happening. The weight usually wins, but not immediately. And as it wins, it has great leverage on the metal tube. That leverage may be our enemy. Aircraft with forward-mounted engines (Piper, Cessna, King Air) almost always nose over and are pulled underneath the surface in a straight down posture. Weight overcomes float.
So what is the posture of aircraft with underwing engines (Boeing, Airbus)? I find two great examples. First is the Boeing 707 in Lake Victoria in Africa, which floated for days, right side up, and never tilted in any direction. The weight never overcame the float—the wing tanks were empty, so it had positive buoyancy.
The second example is US Airways flight 1549, the Airbus in the Hudson River. Initially, that aircraft also floated right side up. There was minimal buoyancy as the tanks contained a lot of fuel and little air. Eventually, the jet sank as it filled with water—the fuselage filled due to an accidentally opened rear door—and the weight of the structure overcame the float, an example of negative buoyancy. Underwing mounted engines have little leverage on the fuselage. They are pulling straight down on the wings.
This brings me to my main point and the significant question. Those in the business jet industry mainly fly rear-mounted, two- or three-engine aircraft. How will they float? I found zero pictures, here.
During my last three type rating training events, the evacuation training centered on escaping through overwing window exits. Two type ratings came in the last five years—the Embraer Phenom 300 and Cessna Citation Latitude. Both of these jets have a water dam located along the floor in front of the main entry door. The dam is raised before opening the main entrance door if you are on the water.
It seems laughable to think this eight-inch dam keeps any water from entering the cabin. But why? Well, think about the battle of buoyancy versus weight. The heaviest part of the aircraft is the engines, and rear-mounted engines and systems mean the tail is the heavy end. Maybe the engineers have determined the float posture requires the water dam because the overwing window exits may not be useable? Aircraft manufacturers need to explain this, and I suggest they have—hence the water dams.
Next time you are on the ramp with your aircraft, stand 30 feet off the wingtip and ask yourself how would this machine float? Use your knowledge of center-of-gravity concepts as you analyze the distribution of weight. It is eye-opening.
In closing, I bring up a sticky subject on radio operations. Frequency spectrums have limits. In the VHF range, multiple agencies own parts of the spectrum and aviation owns 118.0 to 136.97. The Federal Communications Commission says never shall the parts overlap.
In New York on Sept. 11, 2001, the fire department could not talk to the police and vice versa. So I ask the FCC and the FAA why can’t your agencies work together and allow aviation radios to tune in the maritime band international emergency frequency (156.8)? If a crew faces a ditching, a pilot can press the emergency/maritime button on the control head and broadcast on the frequency to make the mayday call to a ship before landing. It takes miles to stop a ship moving at only 10 knots, and every minute counts.
Maybe that button could transmit on 121.5 and 156.8? Then even after you land, you can still talk to the ship. There are great reasons to make this happen. Let’s think outside the box now, instead of thinking about it after we need it.