421 Pattern Work

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  • #84320

    I am hoping to be the owner of a 421 in the next 30 – 45 days (not sure if this will be a B or C model), and I am trying to do some pre-homework. I notice LOTS of thread responses talking about babying the GTISOs, but how does this translate in the pattern when you go from max power to pattern level off speed settings? What is a good speed for the pattern and what settings should be used to attain this?

    #99485
    quote MYarnall1:

    I am hoping to be the owner of a 421 in the next 30 – 45 days (not sure if this will be a B or C model), and I am trying to do some pre-homework. I notice LOTS of thread responses talking about babying the GTISOs, but how does this translate in the pattern when you go from max power to pattern level off speed settings? What is a good speed for the pattern and what settings should be used to attain this?

    Congrats in advance on your upcoming purchase! I would make sure you take any prospective plane up to at least 16,500 at climb power and monitor pressurization, engine temps, MP and FF’s, etc. Bringing along your own pilot with experience in make/model is a good choice too. There is enough aisle space you can switch positions mid flight. A camera also helps. A mechanic with type experience is also a good idea.

    Pattern work is not a good way to evaluate pressurized planes but it is fairly straightforward – it is just happening fast.
    Takeoff: 100%, rotate 95 kts, pitch for 7 degrees, gear up once no runway left
    Upwind: Power pulled back to cruise climb at ~500 ft (or could do a single power change in cross wind)
    Crosswind: In turn at pattern altitude power pulled back to MP 25 something and 1600 rpm, flaps 15 for about 120-130 kts.
    Downwind: Abeam numbers (and cleared for landing) gear down and verified. MP 22 or so. ~ 120 kts
    Base: Flaps 30, ~110 kts
    Final: < 500 AGL Verify gear Flaps to 45. Vref ~100 kts (~90 at lighter weights). Power usually around bottom of green at 1600 rpm.

    I think touch and go’s are a bad practice in a twin. Leaving the gear down is also bad practice.

    The highest workload is typically from upwind to cross wind as this has the biggest power change, attitude change, bank and config change all at once – while watching for traffic, etc. Still very manageable.

    The GTSIO specific info is avoid the prop driving the engine for extended periods. For pattern work, I am not sure it really matters (since it is so short of a time), but keeping the prop rpm lower at low throttle settings helps avoid this. Overall, the most important feedback is to keep all power changes smooth and make sure you are at least as rich as the FF targets (for ROP operation). The crank and counterweights are about 100 lbs – they don’t appreciate quick power changes (even if they are designed to take the abuse)

    Some other tips: Do not compromise your speed for other traffic – go around early or extend your downwind. I would reject any request for S-turns or 360’s as well. Most towered fields get this, but not always. Sometimes they forget your approach speed is faster than the top speed for some of the other traffic.

    Some things to note on your test flights:
    1) The engines/props should be fairly close in thrust from idle to full power. Any big differences (3/4 inch or more in throttle position, or surging, not hitting rpms, FF out of spec, etc I would abort a test flight) – it’s not that these can’t be managed or are inherently bad – but if they have not got the basics down then what else has been missed??? I hold the brakes to 1500 rpm and MP25, then release brakes as I roll power on to 100%. This is a final check of engines and brakes before full power.
    2) Make sure the pilot flying briefs what they are going to do in the event of a takeoff emergency, and any callouts they want you to make.
    3) I would insist on 7 degree max attitude on takeoff. It would be more impressive at 10 degrees or more – and the plane has plenty of power (especially on a lightly loaded demo flight) – but if you do end up single engine the recovery will be much more challenging.
    4) The basics of when has your pilot last flown, when has this plane last flown, how many hours in make/model, is the plane airworthy, is the pilot current, is the pilot covered on the insurance and is the plane insured
    5) Do they have a checklist and have they pre-flighted the plane per the checklist? I would repeat it with them. Some specific things to check – underinflated tires or worn tires, birds nests in the tail or cowls, low battery, hydraulic leaks under the engine or gear (should be zero), big deltas in oil on the underside left vs right (they will be oily), cracks or loose tailpipe. controls free and clear, AP disengages (I would never turn it on in the pattern – but you want to make sure it disengages). Tail feather trim tabs need to be secure without excessive play. fuel stains or fuel smells. check flap cable with flaps down, make sure they are full up for takeoff.
    6) Make sure they do a safety briefing for emergency egress
    7) I would also suggest having them start it up cold with you outside, then do a walk around looking for leaks (especially fuel) or other things unusual. then shutdown and restart with you on board. Note from a cold prime it is not unusual to get fuel streaming from the forward outlets under the cowl (two each side). If one streams fuel the other should as well. These are the most forward outlets under the cowl. Don’t stand behind the props – the huge prop will kick up an amazing amount of air even at idle.

    Hope that helps – I am sure others have advice to add – or corrections to make. 🙂

    Have fun!

    #99510

    Pattern work is not all that big of a deal in the GTSIO. I do it on every initial and recurrent and have never had a customer complain that it caused any problem with their engine. The engine really gets a worse rap than it should. Having flown and maintained two corporately (before I started my training business) I can tell you that the engines were the most reliable component on the aircraft for both 421C’s that I flew. RAM and Continental will tell you that the gearing section is one area where they have few problems in this engine. It suffers the same problems as the other 300/400 series turbo charged engines. It is all about managing the temps. I think the engines will last longer if you fly it most of the time between 10k-20K it is much easier and the temps will generally be much lower. For most trips that is the sweet spot anyway (winglet airplanes do a little better up higher though). The GTSIO is the only Twin Cessna engine that has the overhead (tuned) induction and the incline valve cylinders which makes it the best twin cessna candidate for LOP operations.

    #99514

    The concern about pattern work in the GTSIO is that the fuel flow at different power settings varies a lot and to keep cylinders optimum and minimize byproducts in combustion chamber requires a lot of mixture finesse as you circuit the airport! As long as you are smooth the crank and prop gear are fine, lastly, do not put props forward on final especially if 120 KIAS or more, let the prop drive the crank.

    Get someone very familiar with the GTSIO before you do this.

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