By me
All photos me too, copyrighted
To properly kick off my return here after an unintentional pause of nine months (!), I’ve decided to revisit an aircraft type I had mentioned in passing some time ago – seeing that, by a stroke of sheer dumb luck, I managed to snap TWO in the space of just one week (which is twice as many as I’d managed over the past 18 years). The machine in question – as the post title infers – is the Retractable Gear (RG) version of the common Cessna 172, an aircraft whose rarity and cool factor is matched only by its apparent uselessness and absurdity…
A mint 172RG, in a modern paint scheme, under clear skies on a beautiful summer morning… I could do worse for a pre-dawn spotting session I must admit!
Swinging 80s
To immediately get an idea of why the 172RG stands out like a sore thumb within the traditionally conservative Skyhawk family, it seems best to start off with its main party pieces, as compared to the stock 172P of the same period (1980):
- fully retractable gear
- a longer snout to house the nose gear when retracted
- cowl flaps
- a 180 HP Lycoming O-360-F1A6 w/ constant speed prop (vs the standard 160 HP O-320 and fixed pitch unit)
- a 66 USG fuel capacity (up from the standard 42)
- and a 1,202 kg MTOM (vs the 1,088 of the P)
Performance-wise, the extra grunt (particularly the increased efficiency of the constant speed prop) and cleaner lines meant the RG could pull up to a 20 knot lead over the stock P, with High Speed Cruise pegged at 140 knots. The new prop also made for slightly better after take-off climb performance (800 fpm vs 700), while the increased fuel tankage gave a pretty chunky range boost, from 440 up to as much as 770 NM.
Cutlass #2 undergoing a wheels-up restoration after a (heh) wheels-up landing in Germany. You can definitely tell it apart in a normal Skyhawk crowd!
However, the ~80 kg added by the gear retraction mechanism also upped the empty weight, now standing at 740 kg vs the P’s 660. Normally, this was not much of a payload issue if you took on only your required fuel – but if you went all out and brimmed the tanks, you’d be left with barely 260 kg of headroom… roughly two 2020 adult males, some luggage and all the stuff normally carried around when away from home (additional oil, tow bar, cockpit/wing covers, emergency equipment, survival kits, …).
The higher MTOM also made for longer take-off and landing runs, both up by roughly 70 meters even on concrete; and while some owners have been known to fly them out of rough fields (and even back country strips), it generally goes without saying that the new legs did not take too kindly to prolonged use on the types of runways normal 172s take for granted.
While the main gear legs are no thinner than those on the standard 172 (where they’re set inside streamlined fairings), Cessna’s electro-hydraulic RG systems are quite complicated things and can go bananas even when mollycoddled. As on the 177RG, 182RG and 210, the main legs of first swing downwards and the fold back into recesses in the fuselage (barely visible here). Early 210s – which were the first to use the system – also had main wheel well doors, but they proved problematic and were deleted well before the 172RG appeared
The Cessna Retractable Dance. Go to 0:30 for retraction and 1:30 for extension. You’ll note that the pilot leaves the gear down for quite some time after take-off; the standard wisdom on RG Cessnas is to leave it hanging until clearing obstacles, since the retraction sequence causes so much drag it can noticeably impair climb performance at a critical stage (this is also SOP on airliners during windshear escape maneuvers). Indeed, the main legs drop by a whopping 60 centimetres during retraction!
Maintenance-wise, private owners, commercial operators and various incident reports all tend to agree that the upsides of its commonality with the stock 172 are frequently balanced out by the many gremlins of the RG system – though user experiences vary considerably, particularly when comparing leisure and training ops.
Persistent weak spots and items that require frequent inspection are the main electric-driven hydraulic pump, down-stop pads that (if damaged) may prevent the main gear legs from locking down, and the main gear pivots that are worn out by the legs’ aerobatics during retraction and extension. There’s also the need to periodically cycle the gear on the ground during checks – which requires jacks and additional man-hours – as well as the costs of servicing the propeller governor (though that’s a pretty standard job).
And while none of these are deal-breakers in themselves – the 182RG and 210 say Hiii! – the cost-benefit math of doing all that on a lowly 172 did not make the RG everyone’s cup of tea…
Mission-ready
So, when all was said and done, the 172RG was a cheap & simple aircraft made expensive & complicated for just a few marginal gains – so much that even the fixed gear 210 HP Reims FR172 Rocket could keep up with it in a pinch (and for noticeably less money). What’s more, if you really wanted the “Full RG Experience”, five numbers up was the (slightly) more powerful, (much) more efficient, (oodles) more comfortable and (far) more elegant 177RG Cardinal – an aircraft conceived outright for the touring role, offering 182 series frills without many of its financial chills.
The 172RG thus appears to be – in technical terms – a complete crock. However, outright performance and mass market appeal are not what this airplane is about; its forte was to corner a very specific niche of the training market by offering a suitable and affordable “quick fix” for a problem few manufacturers seemed interested in tackling.
The niche in question was for what’s termed a complex aircraft, a surprising demanding specification that calls for a simple, easy-to-fly, robust and cost-effective airplane that can also boast toys such as flaps, retractable gear and constant speed props – all the complicated and fiddly stuff that future airline drivers are supposed to deal with (did mine on an old, student-weary PA-44, so the full set of traumas is there!)*.
And with the Skyhawk’s 25 years of active service to its name, the type’s well-known middle-of-the-road handling, off-the-shelf components (even the landing gear, nicked off the Cardinal), a reliable and frugal powerplant and a developed global support network, the 172RG had hit all the nails it needed to hit. Even though it would be born on the eve of Cessna’s decade-long single engine production pause, 1,191 would be made between 1980 and 1984… not bad for a niche design!**
* the original specification for complex aircraft had not set a specific minimum power limit; in 1997 however, the FAA set the bar at 200 HP, thus disqualifying the 172RG. However, the type still remains in widespread use as an introductory platform for more complex touring machinery – as well as a charismatic “left field” personal airplane
** though there are frequent parallels with the Beech 24 Sierra and the Piper Arrow, the 172RG is actually not a direct competitor to either. Both designs boast thirstier 200 HP fuel-injected engines (the Arrow with the option of turbocharging), better performance, more amenities – and are generally set up more for the posh end of the touring market; their closest Cessna analogue would be the aforementioned 177 Cardinal. The only aircraft on equal footing with the 172RG was the very first version of the Arrow – the 180 HP PA-28R-180 – which debuted in 1967 and remained in production for only a couple of years before being superseded by the first of the 200 HP models
What’s in a name?
While all of the above ticks quite a few Achtung, Skyhawk! boxes, one more thing remains that is very worthy of mention: it’s name.
While it does say “Cessna 172” on the tin, the 172RG is techno-legally not a purebred Skyhawk – but rather an offshoot of the nearly forgotten 175 Skylark. Billed as the next step towards the larger 182 (a role that would later be filled by the 177), the 175 was in essence an up-market high-trim version of the 1956 172A, fitted with a geared 175 HP Continental GO-300 instead of the standard direct-drive 145 HP O-300. Unfortunately, reduction gearboxes were at the time an unheard of feature on such a small civilian engine, meaning that very few pilots had ever encountered one before. The specific way in which such an engine had to be handled – flown at around the 3000 RPM mark – was so alien and absurd to private pilots that many drove them at the more usual 2000-2200 RPM, leading to a ton of breakdowns, failures and bad PR. By 1962, things had gotten so bad that Cessna was forced to pull the plug on the entire design, and retire both the 175 designation and the Skylark name…
A stunning late model 1962 Skylark with the original GO-300. Note the hump on top of the cowling; the propeller axis had to be raised up in order to accommodate the reduction gearbox without relocating the engine mounts
To salvage at least some of the effort invested in the design, the company decided to keep the 175’s Type Certificate (and some mechanical bits) and use them as the legal basis for all future high-performance variants of the 172:
- the 195 HP R172 Hawk XP
- the 210 HP Reims FR172 Rocket
- the military T-41 Mescalero
- and the 172RG
Traces of the Skylark’s original DNA can still be seen in the R172, FR172 and T-41, since they all sport the tall narrow-track landing gear of the 172A, which would be replaced by the squatter wider-track variant we all know and love on the subsequent 172B.
However, this would not be the end of Cessna’s marketing shenanigans; in 1983, the company would launch the 172Q Cutlass (sans RG), an attempt to “schlepp” on the RG image by fitting the 172P with a 180 HP Lycoming O-360-A4N driving a fixed pitch prop. Quite a rare model today – which did not offer much meaningful superiority over the P – only a handful would ever be built before the Skyhawk family as a whole went into its prolonged 80s coma…
Fixer Upper
While at this point in any normal Achtung, Skyhawk! post I’d go off with a ton of (more or less) descriptive external photos, in this instance I decided to “stay inside”, since the opportunity to snoop around a full-blown rebuild (currently at ~60%) was an opportunity too good to miss! The photos are not my best work – it’s hard to maneuver my 1.91 m frame w/ camera and tripod inside a 172 – but hopefully they’ll be interesting enough for the common avgeek!
I don’t know… it feels something is missing… free from all its kit, the Skyhawk panel looks far more commodious than it actually is! Note the (now very visible) sections for the flight and navigation instruments and the radio stack. Before its wheels-up landing and rebuild, D-EGGF also sported an autopilot (fitted above the glove compartment), and will – when completed – also carry a full set of digital engine instruments. Note also the rudder trim wheel next to the elevator trim; a very useful convenience/borderline necessity with a constant speed prop
A peek “behind the scenes” shows just how many wires, cables, ducts – and even chain drives – there are in a light aircraft. The complexity, weight and maintenance headaches of the average analogue panel have been one of the key drivers behind modern glass cockpit systems built around digital buses and remote sensing systems
Lots of wires… and lots of levers too. With carburetor heat, throttle, prop, mixture and cowl flaps controls, the 172RG could be handful for inexperienced pilots used to the trouble-free operation of the classic Skyhawk (but ideal for the well-meaning masochism of flight training!). Indeed, this was Cessna’s most complicated throttle quadrant short of the 182 (even the 177RG had one level less, being fuel injected)
The most out-of-place level in a Skyhawk: the landing gear handle. One of the more unconventional operational features of Cessna’s RG system is that the “gear up and locked” lamp is – red… which on everything up to and including airliners means either “NOT locked” or “in transit”. Somewhat annoyingly, the light remains continually illuminated as long as the gear is retracted… which is mildly disconcerting from a Q400 driver’s perspective!
Like all RG airplanes, the 172 has a backup gear extension system, whose lever is located under a cover between the front seats. The trick here is that it is just a hand pump, to be used in case the electric one fails (~35 strokes are necessary, according to the POH); it still requires the hydraulic system to be fully operational, and there is no gravity drop or a standalone reserve hydro system. This “unusual feature” is the 172RG’s main Achilles’ heel: the gear is actually held up by hydraulic pressure, and to keep it from dropping, the hydraulic pump occasionally operates in flight to keep the pressure within limits (between 1000 and 1500 PSI). However, if there’s a leak in the system – which seems to happen with some frequency – the pump’s operation will simply dump the hydraulic fluid overboard, eventually emptying the entire system and rendering the gear completely inoperable
The more normal end of the Cessna RG system. The nose wheel doors are mechanically connected to the nose leg so they open and close with gear motion; their biggest operational problem is that they’re quite large and hang low, so it’s easy to damage them if you’re a bit too enthusiastic with the tow bar
Who would have thought that all of this cabling lies hidden behind the teeny panel of the Skyhawk? Another detail unique to the 172RG is the raised floor (best visible below the CDI), necessary to accommodate the main gear legs when retracted. The main wheels however stow behind the normal luggage compartment, so the loss of space there is minimal
Boxes boxes everywhere, not a place to sit… thankfully, the lack of space for maneuvering about with a tripod is taken up by some pretty cool kit: Garmin G5 x2, GMA350, GNC225… should be quite a looker when finished, very much looking forward to trying it out!
As ever, I would like to extend my sincere thanks to Dorian Delić of Medulin Airfield (LDPM) in Istria, for allowing me to snoop through his family’s hangar and drool a bit over D-EGGF!
POST UPDATE – 8 SEP 2021: it may have taken awhile, but I’m happy to report that D-EGGF has been cheerfully flying for awhile now, shuttling around the northern bits of the Adriatic all summer long. To make it even better, I’d managed to catch it recently at Split, making for a proper photo update!
Waiting for its turn to taxi out for the hour-long hop back home to Medulin
Aircraft pictured:
- D-EGGF: c/n 172RG-0301 • mfd 1980 • ex. N107JB
- D-EPAW: c/n 172RG-0757 • mfd 1980 • ex. N6532V, I-ALEU
Sources:
- AOPA – C172RG article
- AvWeb – C172RG article
- Cessna Flyer Association – C172RG article
- RisingUp Aviation – C172P, C172Q & C172RG specs
- Sporty’s Academy – C172RG POH (PDF)
- Sporty’s Network – C172RG differences (PDF)
Changelog:
- 08 SEP 2021: added photo update
Achtung, Skyhawk! 