These Colors Don't Run - Remember 9.11.2001 Equipped To Survive
 Where do you want
 to go on ETS?

Aviation Life Raft Review
Stability - Staying Sunnyside Up

Click on photos for larger image.

Stability - Staying Sunnyside Up

The stability of the raft is critical. Survival accounts are filled with tales of rafts capsizing again and again, usually losing precious supplies and equipment in the process. Lives which should have been saved have been lost due to capsizing.

Stability is a function of center of gravity, ballast, shape of the raft and the sea anchor. All contribute to keeping the raft upright in heavy weather. Individually, they cannot begin to perform as well as if they are considered as a system. The sea anchor and ballast are the two principle devices which prevent the raft from capsizing.

We'll look at both ballast and sea anchors. Ballast can also make initial boarding easier, the Hoover's lack thereof being a case in point, and prevent tipping when bringing an injured survivor on board. Finally, ballast is even more critical when the raft is not filled to capacity. Ballast is also critical in windy conditions when a raft bottom even slightly raised off the water can be easily caught by the wind rushing underneath and the raft capsized in an instant.

We tested inherent stability and resistance to capsizing by putting the volunteers in the raft in various configurations and seeing how difficult it was to capsize the raft. We tested the following scenarios: single survivor getting into the raft alone and two survivors pulling an unconscious survivor into the raft. Then we capsized the raft by moving all survivors to one side and doing whatever was necessary to capsize the raft. This ranged from remarkably easy to quite difficult.

From a practical standpoint, ballast in a raft is limited to the people and equipment in and on the raft and some means of retaining water below the raft to counteract the tendency to capsize or, as seen on the RFD "R" series and large commercial rafts, creation of a suction effect under the raft.

The occupants in the raft are of limited value in terms of ballast, especially so if there are fewer than the rated capacity; if only one or two survive and end up in a raft for four or six or more for example. The heaviest piece of equipment is usually the inflation cylinder and hardware and that is most often mounted on the side of the raft. On the EAM and Hoover single tube rafts this is mounted opposite the entry where it may help counteract tipping tendency while climbing in, but is otherwise not a big help.

There is one point about water ballast that should be made clear, since it seems to often be confusing. The ballast has neutral buoyancy in the water, in other words, it effectively weighs nothing, though it does have mass that resists upward movement because of inertia. It becomes effective as the raft is raised out of the water. With lesser amounts of water ballast, this is easy to see because you can lift the raft clear of the water and see how it gets "heavier." With larger amounts of water ballast, it has enough volume that it prevents the raft from lifting the ballast much above the waterline, so the effect is not as apparent, though the practical effect is obvious.

Numerous maritime studies on raft stability emphasize the importance of ballast in resisting capsizing and improving ride and seaworthiness. How much and what sort of manner this ballast takes, on the other hand, is still quite controversial. While standards vary, on the marine side the need for ballast has been recognized by the regulatory agencies. The TSO, however, is deficient in this regard and has no specifics. It only calls for "water pockets or other means to provide capsize resistance. . ." Based upon what we have seen, interpretations vary and the FAA can be persuaded that virtually any mechanism, effective or not, meets this requirement.

The Survival Products non-TSO'd rafts, EAM rafts and Winslow's RescueRafts have no provisions for ballast and we consider that seriously deficient. The EAM did include two "sea drogues" on short three foot tethers which they say "improves raft stability." You couldn't tell by us. we noticed no difference with or without them. All are easy to capsize under all conditions, a potentially extremely dangerous situation in our opinion and unacceptable.

Hoover's Small Ballast BagThe other rafts we tested offered some form of additional ballast or stability enhancement, with mixed results. On their single tube rafts Hoover suspends four small ballast bags, constructed of the lightweight nylon ripstop canopy material, from the bottom of the raft, around the periphery. The Type I raft has only three to each side. These have a small weight at the bottom to assist in opening after being packed tightly.

Hoover's four "water ballast pockets" hang down from the floor of the raft about one inch and are 9 inches round and 7 1/2 inches deep equaling roughly 1500 cubic inches (6.49 gallons) or 54 lbs. of sea water each. The ballast made the Hoover single tube raft just barely more difficult to tip over, but it was only a matter of minute degree and it was not such a substantial difference that it made any practical difference in ease of capsizing. We rate them as virtually ineffective and perhaps better than nothing, but hardly adequate. On the Type I raft, the three bags were effectively useless, totally unacceptable.

Survival Products

Survival products Ballast BagOn their TSO'd rafts Survival Products includes some minimal ballast. The ballast bags are actually fairly nicely sized at 18 x 14 x 13 and holding 121 lbs. of sea water, there just aren't many of them and they weren't very well constructed. The bags incorporate a weight and one-way flapper valve in the bottom of the bag to help hasten filling, which it appears to accomplish nicely. This is critical since the bags are open on top only on the ends, and then not a lot, the only other place for water to enter. There are no other inflow holes as are typically included along the sides of conventional ballast bags.

They are constructed of lightweight canopy material for sides, buoyancy tube material for the bottom. The lightweight material tore at the seams near the top attachment points. A slight advantage of this design is that the bag(s) become effective quicker than conventional designs since there is a bit less distance between the bottom of the raft and the effective open top of the bag, approximately 3 inches compared to 4 or more for others.

Survival Products Ballast FailureLocated under the center of the Type II raft is a single ballast bag. It proved minimally effective at preventing the raft from flipping during the boarding tests, a big improvement over their unballasted raft, but is otherwise inadequate to resist capsizing. The Type I is equipped with two of the ballast bags on opposite sides of the raft at the entry points. They did an adequate job for boarding purposes, but are otherwise inadequate. Survival Products has a decent ballast bag design, they just need to add more of them and make them a bit more sturdy, in our opinion.


On its older rafts, BFGoodrich used an open bottomed conical "water pocket stabilizer," 12 inches in diameter at top and approx. 3 1/2 inches in diameter at the bottom. This dangles one inch from the raft bottom and is apparently designed to provide some measure of resistance to water flowing through it, thereby offering some stabilization, but it really isn't ballast. Once it lifts clear of the water any stabilization effect is lost, the opposite of what is needed. The old style BFGoodrich rafts were relatively easy to capsize in all configurations, though the 7-man, being much larger, was much better when filled with people. However, if all the people were gathered along the center and one side of the raft it was easy to tip over along its long axis. We would rate the old style BFG stabilizers as ineffective and stability as unacceptable

BFGoodrich Ballast Bag and Holes in BottomThe new BFGoodrich rafts all have four modestly sized ballast bags, 12 x 11 x 11 inches / 1552.5 cu. in. or about 57.5 lbs. each, attached at the "corners" of the rectangular portion of the raft on the larger rafts and equidistant around the circumference of the 4-person. This is a huge improvement over previous BFGoodrich designs. BFGoodrich places five 1-inch holes in the bottom of the bags, allowing water to escape, albeit relatively slowly. Still it just doesn't make much sense to us why you would put holes in water ballast bags. It inevitably reduces the ultimate performance of the ballast and therefor compromises the safety of the raft and its survivors.

Performance on the 4-person raft was adequate, if not exceptional. On the larger rafts the ballast is inadequate and performance mediocre at best. As we've mentioned previously, this minimal ballast is not sufficient to compensate for the shape which makes it particularly vulnerable to overturning if the sea anchor is lost or not deployed properly, an all too likely situation. And, in fact, the sea anchor came loose on our test raft.

Air Cruisers

Air Cruisers BallastAir Cruisers' ballast is unusual in both shape and construction. The bags are 22 x 9 x 11 inches with a rounded bottom and holding approximately 65 lbs. each of sea water. There is a small 3/8 inch drain hole in each end of the bag. A spring wire is fitted inside the trim at either end, helping to do maintain the bag's shape. We had expected this to also assist in quickly deploying the bags when the rafts is inflated, but surprisingly it doesn't seem to make any difference, they dropped down and filled at about the same rate as conventional unweighted bags. The 4-person raft has a trio of ballast bags, the 13-person is fitted with four, both inadequate in our opinion. Both Air Cruiser rafts were relatively easy to capsize.

Rip in Air Cruisers Ballast - typicalThe ballast bags are constructed of lightweight canopy material with buoyancy tube material used only on the ends. The half round inflow holes have reinforcing trim sewn onto the rounded lower portion of the hole. We found tears in the fabric of the ballast bags of the larger raft during our examination, a serious concern. The tears originated in the infill holes at the top of the bags where some essentially square corners in the cutouts would seem to invite propagation of tears and along the seam.


Winslow's GA and optional Cape Horn Ballast BagsWinslow's ballast system comes in two versions, one for its less expensive GA rafts, and one for the TSO'd rafts. Having evolved from Winslow's marine rafts, the ballast system was designed to with an eye to the stringent SOLAS (Safety of Life at Sea International) requirements for rafts used in the North Sea and similar high sea state environments. They were the largest capacity and best performing ballast systems we tested.

The GA rafts are equipped with three large ballast bags, each 17 x 17 x 12 inches / 3468 cu. in. and 128.4 lbs. The ballast bags on their TSO'd rafts are slightly smaller, though still quite large, 17 x 12 x 11 inches / 2244 cu. in. and weighing 83 lbs. each. There are five of these around the periphery of the raft. The total volume and weight of the two systems is very close. While I much prefer the five bag "pentagonal" ballast system because it better distributes the ballast more evenly around the raft and lessens stress on each bag and attachment point, both systems proved very effective in our tests. In fact, the Island Flyer was the only raft, aviation or marine, that our volunteers were not able to capsize by themselves, despite numerous attempts.

Winslow Ballast for TSO'd RaftsA nice feature is the addition of "tripping lines" to the bags. A length of parachute cord is attached to each bag so that they can be pulled up, emptied and tied up for sailing or paddling the raft. While rafts with large ballast bags are very stable, they are also very difficult to paddle or sail since the bags create an enormous amount of drag. The bags can also present problems for a landfall when they can catch on rocks, reefs and such. In use, the lines are tied off to the outside lifeline and can be let go again when necessary and the ballast bags allowed to refill.

The parachute cord used as tripping lines on the rafts we tested was unlike traditional parachute cord we have seen and we didn't like the fact that is seemed attracted to Velcro and would stick to it very easily. While mostly a nuisance, we were happy to see that since our test Winslow has switched over the normal parachute cord for everything and this doesn't exhibit this tendency.

Winslow also offers an approximately 50% larger "Cape Horn" ballast system as an option ($87) for those seeking even large survival margins.

Is the Winslow ballast system overkill? Not in my opinion. The net result was a dramatic contrast compared to all the other rafts. It was very difficult to tip the rafts over. Once this raft is right side up, it isn't likely to go upside down again in all but extraordinary sea conditions. Further, in simulated wave action the raft rode perceptibly better than the other rafts with reduced bobbing. We rate the Winslow rafts' inherent stability as good to excellent and a very big plus in their favor.

The RFD Navigator is the only single cell raft with ballast of any sort, a significant advantage, relatively speaking. It is equipped with three modest ballast bags, 9 x 12 x 7 inches / 756 cu. in. and weighing 28 lbs. each, one in the center of each side and the rear, attached to the floor and buoyancy tube. While a bit small, they do make a difference in boarding, but it is still all too easy to upset this raft.

The RFD "R" series raft eschews traditional ballast, rather it depends upon "suction" for stability. The concept is that the semi-rigid lower buoyancy tube and the raised floor create a plenum which develops suction when any attempt is made to lift it from the surface. When well loaded the concept is reasonably effective. The weight of the survivors helps keep the lower tube in contact with the water so that suction can be maintained.

I have concerns that it may not suffice in breaking crests or very heavy seas or with a lightly loaded raft. With only one person on board, we noted "air" under the leading edge in our wave test, in other words, the suction was broken. With only a single person on board the raft was easy to overturn and there was no notable resistance to overturning. In its present configuration, The suction ballast would have to be considered inadequate. Adding ballast of some sort would be a big improvement and not all that difficult.

Bottom line on ballast is that only Winslow provides adequate ballast, both for the unapproved rafts and TSO'd rafts. BFGoodrich's 4-person is OK, but not nearly the equal of the Winslow. The remainder just don't get it, in our opinion. Now, having said that, Winslow and BFGoodrich do not vary ballast in proportion to raft size. A 4-person raft gets the same ballast as a 12-person. What's adequate for the 4-person is really not nearly as adequate for the larger rafts. Air Cruisers adds a ballast bag on their larger raft, but they are starting further back down the slope, so the sum total isn't very good. We believe that larger rafts require more ballast since they are at potentially greater risk for capsizing in severe weather conditions when lightly loaded. While the longer lever arm helps somewhat, more ballast would help more.

Please support Equipped To Survive with a tax-deductible donation

Aviation Life Raft Review (click to continue to next page)

« Prev. [Previous]
[Next]  Next »

Publisher and Editor: Doug Ritter
Email: Doug Ritter
Revision: 001 October 5, 2000
Webserver courtesy of Pulver Technologies
Email to:

© 1994, 1995, 1996, 2000 Douglas S. Ritter - All rights reserved.
Check our Copyright Information page for additional information.