340 v 421 w/ RSTOL

Home 2024 Forums Opening Section Buying a Twin Cessna 340 v 421 w/ RSTOL

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    I know there is an older similar post comparing the 340 to 421, but I am hoping for some more info.

    I have been a member for about a year in anticipation of maybe getting into twin cessnas. ABout 6-10 times a year I go into a 2600ft ashalt airport with trees on either end.

    Once in a blue moon I go into an 1800 ft grass strip with nothing but water on either end.Vacation spot with family/full load.

    I can do these missions with a seneca II.

    I have been looking at 340 Ram VII’s, or 340’s with RSTOL. Lately though, I have noticed 421B’s with RSTOL ( there are at least 3 on the market right now) the 340 w/rstol have gotten scarce it seems.

    Can I get feedback on:

    1. the real difference in maintenance costs between a 340 and 421B. One post said there wasnt much of one. I would really like to believe that.

    2. any new news on whether the 421 wing spar SID will become anything more?

    3. Given the short runways I mentioned, which machine would you rather uese, the 340a Ram VII ( or similar), 340 w/ RSTOL. or 421 w/rstol, or none of the above?

    thanks great forum. rivals my piper forum.


    I am going to defer most of the response to the folks with a lot more experience than I have, however, I know one question that is burning in my mind after reading your post:

    What is your definition of a “full load”? How long do you want to fly after getting in and out of the short strips (fuel load) and how many butts are you putting in the seats? A 340 is limited to load carrying capability, so that question is going to need to be answered so you can get the best response. Also, in looking at the 421 market for so long (we just purchased ours not to long ago), I can fill you in on some of the 421s with the STOL kits on the market. Two of them are very good buys, if you are willing to make a compromise or two. Shoot me a PM and we can chat.


    Thanks and will do on the PM. For the purposes of this discussion/my questions the aircraft would be at MTOW.


    Speaking from a 340 stand point….I wouldn’t attempt any takeoff from a
    hard surface runway at MTOW (6290lbs) that was any less than 4000 feet. Period.
    Yes the numbers can show you can do it in probably 3200 ft best case
    scenario ( I can’t comment on the RStol numbers as I haven’t flown a 340 that has
    it installed) but you are asking for big trouble at 2600 ft and forget 1800 ft.

    To venture into short runways just takes out too many safety precautions that
    will drastically reduce your flying longevity IMO.

    You most certainly can land in a short distance but with the load you
    want to come out with….. you will not have enough room.

    I would assume the same for a 421.

    Sorry might not be what you want to hear but these planes do a lot
    of amazing things but short field ops is not one of them.


    Thanks Derek. I agree.

    Just to be clear for the others, I am not asking about Derek’s plane ( RAM I) or a non RSTOL 421, the two aircraft he is commenting on. My post concerned the 340 ram vii, 340 RSTOL, and 421 RSTOL. Thanks.


      It’s all risk management. There is more risk as the experience level in the aircraft is low.

      All 3 of the aircraft you mentioned will operate out of an 1800 foot runway under certain conditions. I have done it 100’s of times in each of those airplanes over the last 33 years. But…..

      There is about a 20 second period on the takeoff roll until your over the trees and have Vy, that if a significant amount of power loss is encountered your going to lose the airplane. There are procedures and techniques that can mitigate the exposure but you can’t eliminate them. You will not be given those techniques at a simulator training facility.

      There are snake-oil salesmen everywhere in this industry pushing more speed and performance out of their gadgets, most are unproven smoke and mirrors. Everything is a trade-off. The Cessna 300 an 400 series performance charts have a lot of fudge-factor built into them. They are a good bottom line number.

      Keep’em flying.



      Hi, it would help to know your payload in people and intended destination in distance as the full load is very different between planes. My rule is not to fly in or out of a field outside the balanced field requirements (accelerate/go + accelerate/stop tables). There are others that do this routinely in exchange for a brief period of risk.

      One other consideration is a full loading plane is ~ 7500 lbs and the ground needs to be able to support the weight. Some grass fields might not be ready for this type of loading and you will be damaging the turf and/or putting more stress on the undercarriage.

      for the 2600 ft field, what is the width and what is the tree height? Can you share the identifier? Perhaps someone has direct experience in the planes you are considering?

      Is this a sea level field? what temps? Do you have a performance chart? I would be happy to email you a couple pages of a 421C (stock) table.

      I have not seen anything further on 421C SID’s. That little fatigue damage has been found (and probably more damage caused by complying with the SID) suggests to me that Cessna was overly conservative in their risk analysis.

      Where are you located? have you been up in a 421C or 340? Would be happy to take you flying if you are nearby and I am sure others would as well (+ if you are twin rated it is a good safety pilot opportunity 🙂 )


        Good Morning
        I fly my 340 Ram VI out of a 2600 ft paved strip with trees at both ends.
        I feel relatively comfortable with that situation at almost gross.
        The field elevation is 740 ft but would not like to depart on a 90 degree day.


          I think if you told you insurance agent what your plans are, you would not get insured. Insurance underwriters have enough problems with pilots who use book numbers for their takeoff and landings so I would suspect they don’t need you to give them more grief. Buy a Caravan or Kodiak so we don’t have to read about you and your passengers in the obit column. Risking your own life is one thing, but 4 or 5 innocents is another.


          So this is what passes for rational discussion and cordial information exchange at the Twin Cessna Flyer? Remarkable.

          If you read my original topic starter, I hope you found that as a non-owner member with a good deal of twin experience, ( who actually bought a second twin cessna flyer membership for a friend with a 414 who had not heard of your group), I asked a reasonable question about highly modified versions of the type, and that I was not sold on any Cessna to fit the mission I described. I simply asked if the modifications would make The type more suitable for the mission, or not ( remember the ‘ none of the above’ option I laid out) That’s It.

          Then due to Welsh’s needlessly inflammatory comment we wind up on the Crazy Train here. I waited to respond until now to see what other members or the moderator had to say about this last “post”, but read nothing. Telling. It’s kind of an odd way of attracting membership, preserving the type, and furthering aviation safety.

          Anyhoo, Until now, I think the thread was mildly helpful, although the first two sub questions weren’t really touched on well.mAs you can see, I did have to redirect the discussion once to get back to the questions I posed, but there the poster didn’t assume facts not known to exist and wasn’t arrogantly judgmental, assuming motives or “plans” into what I thought was a well-thought out, objective and sterile topic question. And as you see from the posts there are differing observations about the use of modified 340’s/421’s.

          To recap the other two questions I posed, does anyone care to comment (assuming you are sane and/or not overtly miserable) on:

          1. The real world maintenance cost difference between the 340 and 421 types.
          2. Any new thoughts on the wing spar SID

          And if anyone who actually has RSTOL or Vi/VII short field experience wants comment on short field ops that would be welcomed.

          I do want to thank Zac, Derek, Richard and Pat for saring there experiences with the types here and offline.



            A Reminder: Rule #1 of this Forum as posted in the Welcome Section: “We all practice courtesy and civility”. To me, that means treating people as you would if you were talking to them in person. In fact, it’s highly likely many TTCF members will eventually meet if you attend our seminars or our Annual Meeting next year.

            IMO, the proper way to respond to someone who proposes something you think is risky is to say something like “That’s not a risk I would take for these reasons…..” Period. If you think they are proposing something truly dangerous, then PM them and state your case.

            The proper way to respond to someone whom you think has insulted you on the Forum is to ignore them. If you need to retaliate, do it privately. If you have a need to save face, simply state on the Forum “I’ll PM you.” Then everyone knows you confronted your accuser.

            I have watched other Forums deteriorate due to lack of civility. It will not happen with this Forum.


              I have over 20,000 hours in twins, jets, tail draggers, turboprops, and lots of mountain flying and I ran a business that retrieved broken bodies and airplanes for insurance companies due to some real stupid piloting; all in the mountain west. Just the idea of taking any twin short of a Twin Otter into the environment that was suggested just doesn’t sit well with me. If the poster wanted some suggestions for the mission, I gave him the Caravan and Kodiak. If that didn’t sit well, I can’t help the fella out.


              I owned a Cessna 320 with a RAM I conversion(300hp) and RSTOL. I did not measure take off roll, but I can tell you it made a significant difference. I would think that there would be a large difference on a 340 or 421 as well. The only way to know for sure is to fly one. There is a 421B for sale in Pueblo, CO which has the RSTOL you might want to talk to them about performance. The aircraft is advertised in both TAP and Controller.

              Good hunting,


              The Seneca II is ~ 4500 gross, 2850 empty. 100 gallons? Range ~ 600? A 421C would offer more useful load even at full fuel. For a range of 600 you would be closer to half fuel.
              At half fuel and ~1000 lb people and cargo you would be 1000 lbs under gross in 421C. If you could take off with even less fuel from the 1800 ft strip then you would be better off.

              Other’s have experience with this short of field, it is beyond my experience and tolerance for risk. The ground roll alone would be longer than 1800 ft much above sea level and/or closer to gross (not including grass impact). I can understand your interest in RSTOL!

              The other challenge is ground handling at smaller fields as the 421C is twice as heavy!


                Will through this offer out to anyone interested.

                I have a stock1976 Cessna 421C with V’g operating on a FAR135 certificate. This airplane is set up for ultra long overwater operations. By ultra-long, I mean Honolulu to Boise Idaho. We have experience in operating the airplane in all corners of the envelope.

                We also, have a Cessna 421B with a Robertson STOL. This airplane was flown by the owner around the world a few years ago. It is for sale and we will help you fly it home. You will fill very comfortable in the airplane when you get it home.

                We are in Paradise on the island on Oahu. I have Operated, Instructed, Demonstrated and Maintained Twin Cessnas since 1977.

                Come for a vacation in Hawaii and I will fly with you in each airplane all you want. We have an insurance approved initial and recurrent training program for all twin Cessna’s.

                We will rent you the airplanes for $1000.00 per hour. I’m free, will fly for food.

                Keep’em Flying



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