by Paul Bertorelli
When Bonanza owner Larry Hofmeister told us he had intended to ride out the vicious winds of Hurricane Charley in his hangar at Punta Gorda, Florida last August, we thought hed lost touch with reality. Were as fond of our airplane as the next guy but babysitting it through a Category 4 hurricane doesnt rise to the top of our to-do list.
Yet when Hofmeister arrived at the airport the day after, both his Bonanza and the hangar that housed it sat serene and intact amidst a scene of utter destruction elsewhere at Punta Gorda, with some 150 aircraft smashed to scrap metal by Charleys fierce 130-MPH-plus winds. The first question is glaringly obvious: what kind of hangar does he have and, more to the point, what do owners need to do enjoy similar protection from a major hurricane? The short answer is to insist on a hangar built to Floridas new post-Andrew building codes or add steel bracing and pay for a good door.
Fight or Flight?
As Charley approached on August 12th, owners along the west coast of Florida faced a difficult decision: fly the airplane out of harms way or secure it in the hangar. Many who chose the latter lived to regret the decision, for Charleys intense gusts shredded older hangars within an hour of its landfall at Charlotte Harbor. Even commercial hangars supposedly engineered for hurricane winds succumbed.
We toured the Punta Gorda ramp twice, once the day after the storm and again three weeks later, when we had time to more closely examine the damage and study the failure patterns. Before our second visit, we spoke with several experts familiar with hangar engineering, including Jesse Douthit, who oversaw the recovery for Kermit Weeks air museum after Hurricane Andrew all but destroyed it in 1992. Douthit supervised the design and construction of Weeks new hangars at the Fantasy of Flight facility in Polk City, Florida.
He told us the typical T-hangar has a sound steel center structure but is typically much weaker around the perimeter walls and, especially, the doors. Just as Douthit had seen at Kendall-Tamiami Airport during Andrew, the doors-specifically sliding doors-proved the weakest link at Punta Gorda. As shown in the photos here, nearly every sliding door on the airport was lifted out of its tracks and blown in. Some sailed yards across the airport and one wrapped itself around a utility pole.
Once relieved of their doors, hangars failed progressively, with exterior walls and downwind doors departing and interior partitions crumbling. Many airplanes were blown right out of the hangars and found dozens of yards away, usually in tatters. The most windward row of T-hangars-constructed in the 1970s-was blown completely down, leaving a debris-strewn concrete pad but little else. Hangars further downwind lost doors and airplanes but roof structures generally remained in place, just as Douthit observed at Kendall-Tamiami. During our tour, Larry Hofmeister, who is president of the airports tenant association, showed us something interesting but not surprising: some of the principle steel members in the hangars were corroded and thus had a fraction of the strength they had when new. We don’t know if these were factors in failures but if you own an old hangar that youre depending on to resist hurricane winds, it might not if fasteners and steel are rusted, as they likely are in parts of the country susceptible to hurricane-force winds
Although its too soon to declare Floridas post-Andrew building codes an unqualified success, hangars built to those standards-as Hofmeisters year-old hangar was-clearly fared better than older hangars. Specifically, the code requires only minor structural changes, but older hangars were probably built to far less stringent standards. Doors and structures must resist up to a 110 MPH sustained straight-line wind with a three-second 120 MPH gust. Hangar doors in the Florida Keys and south Florida, must resist between 146 MPH and 155 MPH gusts.
Hofmeisters hangar is equipped with a robust, single-piece steel frame HydroSwing door raised and lowered by a pair of long-stroke hydraulic cylinders. HydroSwings Jason Wing told us the 120 MPH door sells for about $5700, including the lift mechanism. Another $300 buys the 155 MPH door.
Curiously, much of the doors wind resistance comes from so-called cane bolts which are heavy sliding pins along the base of the door. That, says HydroSwings Wing, is the only part of the door not tied directly into the hangar structure. We were surprised to learn-and so was Wing-that the Punta Gorda hangars had cane bolts but the holes in the slab werent drilled to accept them. Hofmeister says the reason for this is unclear but the fact that the doors survived anyway is testament to their sound construction.
The hangars themselves were designed and manufactured by Dean Steel, one of the first companies to build metal buildings to the new Florida codes. Deans vice-president of sales, Jim Taquette, told us that building hangars to Floridas new codes requires only about 5 percent more steel and weight and a like amount of cost.
In other words, in terms of the total project cost, a hurricane-secure hangar adds a trivial sum to the bottom line. Taquette says that the principle change in the code affecting hangar construction relates to eliminating overstressing, which allowed engineers to claim up to 30 percent more peak load capability than some components could actually handle. In other words, hangars built to the new codes allow no undersized components for the claimed wind load.
In touring Punta Gorda, we also noticed that another type of door fared well: the bi-fold, electrically operated design typically found on Ful-Fab steel hangars but also made by others, including Hi-Fold. We saw only one of these fail and it did so only partially due to a heavy debris strike, without significant damage to the hangar interior. The reason is obvious: under wind load, the bi-fold distributes its load evenly to the rest of the hangar structure, in much the same way the HydroSwing door does. Bi-fold doors are usually-but not always–equipped with cane bolts, although these may be modest in size. Jesse Douthit told us if he were building a T-hangar, he would specify the largest solid-steel cane bolts practical for, typically, if these doors fail under wind load, theyll kick in at the bottom, a failure cane bolts are designed to prevent. Deans Taquette says sliding doors can resist hurricane wind loads if engineered correctly but our view is that swing or bi-fold doors are better.
What to Do
Hurricane Charley taught aircraft owners and residents of southwest Florida a bitter lesson. No major hurricane had struck this part of Florida for more than 40 years and heretofore, it was assumed that any storm would quickly weaken after landfall. Yet Charley remained a Category 2 storm we’ll into central Florida, wreaking extensive and expensive havoc. Many owners simply hadnt heeded the lesson of Hurricane Andrew and assumed-wrongly-that their hangars could withstand a strong storm.
Owners in the path of a hurricane always face a difficult choice and, ultimately, flying out of harms way may seem too expensive or too inconvenient to consider. That means the hangar becomes the last line of defense and, as was revealed at Punta Gorda, many arent up to the challenge unless theyve been built recently and perhaps not even then. In Florida, that would be after 2001, when more stringent codes came into play.
Elsewhere-all along the Atlantic and Gulf coasts-building codes and wind loading requirements vary. Our view is that if youre building a new hangar or can afford to upgrade an older one, build to the Florida code or, at minimum, specify additional steel structure during manufacture.
For example, says Dean Steels Taquette, specify girts and purlins on 3 1/2 foot centers rather than 5-foot centers and specify 24-gauge rather than 26-gauge cladding. Ask the contractor to increase the size and decrease the spacing for fasteners and specify the largest cane bolts you can get.
Unfortunately, hangar projects go to the lowest bidder, thus to remain competitive, manufacturers don’t include these additional materials in their bids.
Taquette estimates that such changes will add 5 per cent to the overall project cost. If a quality hangar costs $50 a foot all-in, you’ll spend an additional $2500 for such upgrades. That strikes us as chump change in exchange for the peace of mind of knowing that your hangar will survive the big blow and not having to suffer the trauma of watching the wreckage of your airplane trucked off while you await an insurance check.
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