Hard-Landing Damage: Firewall, Gear Repairs

Hard landings happen, but major damage to the airframe can go unnoticed. Look closely for firewall, landing gear and wheel damage when shopping used airplanes.

Sooner or later your used aircraft search will find an airplane that’s suffered a so-called hard landing. While that’s the sugarcoated word for damage history, in some circumstances this is hardly a deal breaker. Other times, it’s best to walk away, especially if the damage has gone unnoticed or left unrepaired.

What’s the definition of a hard landing, exactly? Few service manuals are specific other than describing it as the airplane touching down with an excessive sink rate. But what matters is the type of damage sustained, how it’s repaired and its effect on resale value.

That’s what I’ll cover in this article, paying close attention to high-dollar repairs like bent firewalls, landing gear mounts and other major airframe components. I’ll cover damage to tailwheel airplanes in a separate article.

Pancakes and Wheelbarrows

I won’t analyze the reasons for landing hard, but most firm arrivals take two common forms—the pancake, where the plane smacks hard on all three wheels from slowing to a stall too high above the runway, and the more dramatic wheelbarrow, where the aircraft is in a nose-down attitude and the nosewheel strikes first. Since the nosewheel is the least robust gear component on most tricycle gear aircraft and wheelbarrow landings are common, I looked at them carefully from a damage standpoint.

I recently followed a forum thread on this topic and found it interesting that some relatively experienced pilots exclaim in disbelief that they bent the firewall on their “slightly botched” landing (the airplane was a 1966 fixed-gear Cessna 182). While this is generally a pricey mistake, not all aircraft are created equal in firewall damage susceptibility.

In contrast, the robust gear on the original Beechcraft Bonanza was drop-tested at a simulated 1200 FPM to meet aircraft carrier landing specifications (controlled crashes, Navy pilots chide) for the Navy. At the time, Beech was hoping for a Navy military trainer contract (T-34). The Bonanza is also certified in the utility category. But that’s not to say that the Bonanza hasn’t had its share of issues; there just aren’t the number of landing gear crunches or bent firewalls seen with others. After logging over 2000 hours in various Bonanzas—old and new—plus in the T-34, I can attest to the robustness of the gear. That said, all certified aircraft must meet a minimum FAA design standard, but there is a certain variation in how the nosegear strut is mounted to the aircraft. Let’s look at that closely.

Nosegear Mounting

Nosegear mounting takes three common forms on typical GA aircraft. The first is common on the most popular fixed-gear Cessnas, where the nose strut is attached to a primary structure—the stainless steel, thin, reinforced firewall. This is seen on the fixed-gear models of the 172 Skyhawk, the 177 Cardinal and the 182 Skylane. The Cessna 150/152 series utilize a different method in which the strut is attached to the tubular steel engine mount. Thankfully, it’s quite rugged and designed we’ll for the training environment.

On Piper Cherokees, the nose strut is attached to the tubular steel engine mount. That means the engine mount would absorb the initial damage in a hard landing, but it could also damage the firewall and engine mount if the impact were hard enough. Don’t underestimate the cost of replacing a bent engine mount, as welding is a specialized task and can be major work.

Worth mentioning is that the Bonanza is different than most all others, including its Skipper, Sport and Sundowner siblings. That’s because only the Bonanza and its variants (the Debonair, for example) employ an aluminum tub attached to the firewall with a raised aluminum section, allowing room underneath for the retracted nosegear. The tub runs the length of the engine and the engine mounts to the tub much the same as on other aircraft, where the engine mounts to a tubular steel engine mount. The nosegear is totally separate under this aluminum tub. It is a robust structure, but can certainly be the cause of grief during some engine maintenance—take it from someone who maintains his own Bonanza.

Is It Broken?

Hit hard? Don’t fret, because not every firm arrival means the aircraft sustained damage. But if you hit the runway hard enough to wonder if you bent or broke something, then you probably need to have a qualified tech look it over before you fly it again.

Still, there are things you can do to lessen the blow of landings gone wrong and it starts with good maintenance. In particular, this means proper upkeep and preventive maintenance of the landing gear components. Touch down hard enough and you’ll want to start with a thorough inspection, which could mean putting the aircraft on jacks. For retracs, it also might include a landing gear swing. But before going to the shop, eyeball it yourself.

Start at the nose with a visual inspection and preferably remove the cowling to look for any signs of damage to the firewall. It might be tough to spot, but any wrinkling is a cause to call in a mechanic. It is essential to not fool yourself, but rather err on the side of caution if there’s any doubt. The aircraft service manual (which I recommend you have on hand) is a good place to start.

Many service manuals I have reviewed have a section dedicated to evaluating hard landing damage. It starts with checking for signs of damage to the paint, although a visual inspection of the painted surfaces alone does not guarantee that there isn’t damage. Of course, an owner would be we’ll served to have a good idea of what the airplane looks like in an undamaged state to make comparisons easier. That’s not always the case when shopping for a used airplane.

If at first you spot no skin wrinkles, the next step is to stand away from the aircraft and see if the wings are still level and it sits in what looks to be a level attitude. Be sure to do this on level ground, of course. Do some ground running, too, but taxiing isn’t a sure way to spot damage

According to feedback from several shops during my research and from my own experience, the aircraft may be damaged beyond economical repair in a hard landing and have no outward appearance or symptoms of major damage. For that reason, I never suggest underinsuring. When it comes to hull damage consider that the insurance company may total the aircraft in the event of an accident costing more than the hull insurance. A bent firewall or engine mount typically constitutes a major repair. Moreover, firewall damage hardly ever occurs as isolated damage. Associated structures may be damaged as well, as might other systems that you may not initially consider. These include bracketed control pulleys attached to the firewall structure, which could have a change in tension as if the firewall bends. But there’s more than the firewall to consider.

Hit hard enough and tires, wheels and struts may be damaged, sometimes not even identified during the annual inspection. The most proactive owner may keep abreast of aircraft service bulletins and ADs, but after 46 years owning and maintaining aircraft I’ve learned that an annual inspection (especially a flat-rate annual) isn’t always a guarantee of ironclad airworthiness.

Know Thy Design

It’s easy to use the fixed-gear Cessna 172/182 in examples of hard landing damage, but my intent is not to single it out. The large numbers of these aircraft produced combined with greater than a half century in service tends to disproportionately show bent firewall accidents perhaps more than less popular models, or at least ones with shorter time in service. But it’s worth contrasting this gear design with that of the fixed-gear 177 Cardinal, with a nose gear that also mounts to the firewall. In my research, shops experienced with Cessna repairs stressed to pay close attention to the forward cabin side skins on a fixed-gear Cardinal during a prepurchase inspection. That’s because there’s limited structure behind the firewall for direct support.

Worth considering in the training environment is that the 177 Cardinal’s elevator design differs from other 100-series Cessnas and is partly responsible for running out of elevator effectiveness in some landing configurations. I have some time in all models of 177s and found that the early models can be a bit more demanding in landing without the right training.

What I’m getting at is some aircraft have a reputation for being prone to firewall damage, but some of that is affected by loading configurations such as only the pilot and front seat passenger being onboard, tending to make some aircraft more nose heavy. As a result, a firewall-mounted nose strut may be more prone to causing firewall damage in the event of a nose-first landing. But it isn’t a reason to avoid a given model. In my view the problem is more one of proper training and pilot awareness of the specific model and cabin load configuration, as we’ll as fuel quantity and its effect on CG.

Modifications can help, as Cessna figured out early on. Issued in 1971 and affecting older Cessna 182 models from 1962 to early 1970, Cessna SE71-5 pertains to a service kit that beefs up the firewall strut mounting assembly. The kit was incorporated into factory models from later 1970 and on (gross weight increase to 2950 pounds). This kit not only includes special brackets, but also requires a special high-temperature sealant to ensure certified fire and gas leak standards, as we’ll as use of solid shank rivets to ensure factory certification standards are maintained. Installation of this kit uses 11 pages of instructions. It was estimated to take 75 man hours to install the kit including engine removal. While the entire kit is no longer available, the metal parts are available separately.

Tires, Wheels and Struts

A hard landing may not result in aircraft damage at all if its wheels, tires and struts are maintained to high standards. Walk down any ramp and you can spot airplanes with nosewheel struts sitting barely an inch from bottoming out. You’ll also see the opposite—overinflated struts. These aircraft are much more vulnerable to hard-landing damage.

If a strut is too low it will translate into early metal-to-metal contact with adverse consequences to the airframe. If the strut has the improper air-to-fluid ratio, the strut will perform poorly. In fact, just taxiing with a deflated strut may cause damage constituting a major repair.

Strut maintenance is normally not a pilot DIY item since most struts require access to high-pressure air at the airplane, and a portable air tank is typically insufficient.

Tire blowouts are quite rare under most circumstances, including hard landings. That’s of course provided the tire is in airworthy condition, meaning no cord is visible through sidewalls, for example. Weak sidewalls also contribute to a reduction of landing cushioning, as does under- or over-inflation. Another problem is a tire being the wrong ply rating (too low or too high ply rating), which contributes to too little or too much cushioning on landing, as we’ll as during taxiing. The aircraft type certificate data sheet, available on the FAA website, has valuable information on the approved components, speeds and weights under which your aircraft is certified, including the tire ply rating.

Locking a brake on the mains can destroy a tire in a few seconds or cause loss of aircraft control. In a poorly maintained airplane it may also cause the nosewheel to collapse. Locking a brake can be from improper maintenance or overzealous brake application. Small planes do not have anti-lock brakes, although newer brake technology makes it more difficult to lock up the brakes. Berringer, for example, offers a line of modern brakes, wheels and tubeless tires that might be worth the investment.

Wheel failure is a possibility in a hard landing, especially for wheels that are poorly maintained. Generally, wheels do not tend to bend but rather break. Hasty annuals can skip items that generally look all right on the surface, such as wheels and tires, but they could be ready for failure. Check for missing paint, corrosion and hairline cracks on wheels. Unless you change your own tires you will not know the condition of the through-bolts that hold the wheel halves together. The visible condition of the outer wheel is a good indicator (but not a guarantee) of the inside condition. Repairs to wheels, including welding, constitute a major repair.

Choose Your Battles

It goes without saying that employing a mechanic with extensive repair experience on the aircraft model you’re considering is imperative. Their fees to handle the prepurchase evaluation will be a bargain compared to getting stuck with an airplane that has a damaged firewall or repairs done incorrectly. The same goes for bargain finds that have been sitting for long periods of time, where corrosion takes its toll and can lurk on wheels and other critical components.

If you must go it alone, for starters be sure to go over the aircraft carefully (including the firewall) looking for skin wrinkles, the use of pull-through rivets on the firewall’s structure, uneven rivet repairs, dents or unchecked corrosion anywhere. It should be easy to spot a shoddy repair, but difficult if not impossible to spot a good repair.

A title search, researching FAA 337 forms, a relevant AD search, checking both the FAA incident reports and NTSB accident reports can tell a lot about the history of an aircraft, as can maintenance logbook entries, of course. The likelihood of finding a 40-year-old airplane with no damage history is slim, but with any repairs, particularly major ones, be sure they were properly logged. As I said earlier, quality repairs to landing-induced damage should not eliminate the plane from consideration, but it is a point to begin negotiation if you know the market. Type clubs are a huge resource.

If you do strike a deal on an aircraft that has damage needing repair, you might find yourself hiring a ferry service to move it (after securing a maintenance ferry permit) since it might not be airworthy. Some shops specialize in transporting, ferrying and repairing. For example, Beegles Aircraft Services (www.beeglesaircraft.com) offers a complete turnkey service (including disassembly and transport) and specializes in major structural repairs. Tennessee Aircraft Services (www.tennesseeaircraft.net) is another I can recommend. There are others.

Last, if you want to avoid having to deal with landing damage, choose your battles and the right airplane for the job. During one Alaska trip where our gaggle of five airplanes landed at many remote and unimproved runways, our flight leader bravely landed first to advise the rest of us on any unusual conditions. He had over 2000 hours in his beloved Mooney and still ended up doing a whoop-de-do on an undulating dirt strip. We watched from above as his airplane hit tail first and then on the nosewheel, damaging the fuselage and wrinkling the aft fuselage, which signaled internal damage. When you push the envelope, sometimes the conditions bite back. Luck favors the prepared.

Contributor Kim Santerre was Editor of retired sister publication Light Aircraft Maintenance and is a 20-year Beech V35B Bonanza owner based in Virginia.