# DASH 8 AND TOD (top of descend)

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hiI have the dash 8 of pss, a great add on, really; but I have a question:In the FMC, after insert SID & Star and being in the cruise's phase, I can see somewhere of FMC the TOD (point for a secure descend calculate for the FMC)?ThxBest regards!Jos

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Hola:As far as I know, the DH8C simulated FMC has no vertical navigation capability. You'll need to estimate the TOD by rule-of-thumb (or if IFR under ATC control descend when instructed).Suerte,George

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I love the Dash, it sure is a favorite. To begin your descent, try this:The height you are now at (minus) the height you want to be at for your destination (times 3.5). Just use the 'thousands' only, Here:Your at FL220 and you want to descend to 3,000 feet.22 - 3 = 1919 x 3.5 = 66.566.5 miles from your arrival, begin your descent at around -1800 feet per minute.Of course there are many other factors, but this is easy and will get you in with reasonable accuracy. Not perfect, but it will help you out when no ATC is around.PS: Gear Down!

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Steveark:You may have made life overcomplicated for yourself. Using the 'times 3' rule at F220, you get (3x19) = 57. Add an extra 5 or so nm so to allow for error and to give yourself time to level out and slow down, in this case starting to descend (say) 65 nm out. You'll want to pull back on the power, obviously, but don't lower the gear (except in an emergency descent)! The gear generaly goes down once you've slowed to about 160, intercepted the localiser and the g/s comes alive and is 1-2 dots above centre. Aim to slow to 120 kts (depending on weight) crossing the threshhold.Best,George[EGKA]

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I fly a Dash 8 and just use 3 x height.So for 19000 to lose, start descent at 57nm. There is no need to add anything for error as a 3 x profile allows for plenty of wiggle room.For VS use 1600fpm initially until the speed has stabilised, then use groundspeed x 5 + 100.So if groundspeed is 280 kts. VS should 1500 fpm (280 x 5 + 100.)I find the easiest way to do it is to round the groundspeed up to the nearest multpile of twenty then halve it.So if groundspeed was 250 kts, round up to 260, divide by 2 and add a zero to get 1300 fpm VS. This is just the same as multplying by 5 and adding 100.When closer to the airfield you should transition to a 3 x distance = height profile, this is slightly closer to a 3 degree slope than the 3 x height = distance version. The real Dash decelerates in the descent with no problems I don't have the PSS version so don't know how well it models that side of things.Edit: I DO have the PSS version (didn't realise it was the Just Flight one) and it decelerates ok on descent, just bring the power back to idle and it slows down quite quickly (IMO the PSS version is quite underpowered and doesn't achieve the IAS in flight that it should for a particular power setting.)Also, older versions of the UNS FMS used in the Dash 8 didn't have much in the way of VNAV. They certainly don't have any depiction on the EHSI of a TOD point.

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CW has it spot on, that's what we use on the Q400. Incidentally the Q400 uses the newer UNS-1E FMC with VNAV capability, we do not get a TOD point in ARC mode either, plus there is no autothrottle as expected. VNAV is against company SOPs so we can't use it.D777

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Well I tested it today and we do indeed get a little white circle come up for the TOD point, they say you learn something every day, how true ;)

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We have the UNS1E on our 200s and 300s. It doesn't have a TOD point on the EHSI map for VNAV so it might be a function of the Q400's MFDs.Jon

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