qucshelp: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/bin/qucshelp - from package: qucs

You may install the required package with command yum install {package}

Error in other languages:
qucshelp: bevel nie gevind nie
qucshelp: comandă negăsită
qucshelp: comando não encontrado
qucshelp: commande introuvable
qucshelp: command not found
qucshelp: käsku ei ole
qucshelp: không tìm thấy lệnh
qucshelp: komanda nerasta
qucshelp: Kommando nicht gefunden.
qucshelp: kommandot finns inte
qucshelp: komut yok
qucshelp: nie znaleziono polecenia
qucshelp: níor aimsíodh an t-ordú
qucshelp: no se encontró la orden
qucshelp: no s'ha trobat l'ordre
qucshelp: opdracht niet gevonden
qucshelp: parancs nem található
qucshelp: perintah tidak ditemukan
qucshelp: príkaz nenájdený
qucshelp: příkaz nenalezen
qucshelp: команда не найдена
qucshelp: командата не е открита
qucshelp: 命令找不到
qucshelp: コマンドが見つかりません